The material described by ErFe6Sn6 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Fe(1), four equivalent Fe(3), four equivalent Fe(5), one Sn(2), one Sn(5), two equivalent Sn(1), two equivalent Sn(3), and two equivalent Sn(9) atoms to form distorted ErFe12Sn8 hexagonal bipyramids that share corners with four equivalent Er(1)Fe12Sn8 hexagonal bipyramids, faces with two equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, faces with two equivalent Er(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the second Er site, Er(2) is bonded to four equivalent Fe(2), four equivalent Fe(4), four equivalent Fe(5), one Sn(3), two equivalent Sn(10), two equivalent Sn(5), and three equivalent Sn(8) atoms to form distorted ErFe12Sn8 hexagonal bipyramids that share faces with six equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with two equivalent Er(1)Fe12Sn8 hexagonal bipyramids, and faces with four equivalent Er(2)Fe12Sn8 hexagonal bipyramids. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(9) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, and faces with four equivalent Er(1)Fe12Sn8 hexagonal bipyramids. In the second Fe site, Fe(2) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(4), two equivalent Sn(10), two equivalent Sn(7), and two equivalent Sn(8) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with three equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, and faces with four equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(5), one Sn(1), one Sn(2), one Sn(3), one Sn(4), and two equivalent Sn(9) atoms. In the fourth Fe site, Fe(4) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(5), one Sn(5), one Sn(6), one Sn(7), one Sn(8), and two equivalent Sn(10) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(4)Er2Fe4Sn6 cuboctahedra,  a faceface with one Fe(4)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra,  a faceface with one Er(1)Fe12Sn8 hexagonal bipyramid, and faces with three equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(3), one Fe(4), two equivalent Fe(5), one Sn(10), one Sn(3), one Sn(4), one Sn(5), one Sn(6), and one Sn(9) atom. There are ten inequivalent Sn sites. In the first Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Er(1), two equivalent Er(2), two equivalent Fe(4), and four equivalent Fe(5) atoms. In the second Sn site, Sn(6) is bonded in a 6-coordinate geometry to two equivalent Fe(4) and four equivalent Fe(5) atoms. In the third Sn site, Sn(2) is bonded in a 7-coordinate geometry to one Er(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the fourth Sn site, Sn(7) is bonded in a 6-coordinate geometry to two equivalent Fe(4) and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(8) is bonded in a 9-coordinate geometry to three equivalent Er(2), two equivalent Fe(4), and four equivalent Fe(2) atoms. In the sixth Sn site, Sn(9) is bonded in a 8-coordinate geometry to one Er(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), and one Sn(9) atom. In the seventh Sn site, Sn(10) is bonded in a 8-coordinate geometry to one Er(2), two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(5), and one Sn(10) atom. In the eighth Sn site, Sn(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the ninth Sn site, Sn(3) is bonded in a 9-coordinate geometry to one Er(2), two equivalent Er(1), two equivalent Fe(3), and four equivalent Fe(5) atoms. In the tenth Sn site, Sn(4) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(5) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er(FeSn)6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   19.204
_cell_length_b   19.204
_cell_length_c   5.416
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   153.035
_symmetry_Int_Tables_number   1
_cell_volume   905.725
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Er  Er0  1  0.190  0.810  0.250  1.0
  Er  Er1  1  0.810  0.190  0.750  1.0
  Er  Er2  1  0.937  0.063  0.250  1.0
  Er  Er3  1  0.063  0.937  0.750  1.0
  Fe  Fe4  1  0.500  0.000  0.500  1.0
  Fe  Fe5  1  0.000  0.500  0.500  1.0
  Fe  Fe6  1  0.500  0.000  0.000  1.0
  Fe  Fe7  1  0.000  0.500  0.000  1.0
  Fe  Fe8  1  0.754  0.754  0.500  1.0
  Fe  Fe9  1  0.754  0.754  0.000  1.0
  Fe  Fe10  1  0.246  0.246  0.500  1.0
  Fe  Fe11  1  0.246  0.246  0.000  1.0
  Fe  Fe12  1  0.565  0.940  0.250  1.0
  Fe  Fe13  1  0.940  0.565  0.750  1.0
  Fe  Fe14  1  0.435  0.060  0.750  1.0
  Fe  Fe15  1  0.060  0.435  0.250  1.0
  Fe  Fe16  1  0.308  0.183  0.250  1.0
  Fe  Fe17  1  0.183  0.308  0.750  1.0
  Fe  Fe18  1  0.692  0.817  0.750  1.0
  Fe  Fe19  1  0.817  0.692  0.250  1.0
  Fe  Fe20  1  0.630  0.879  0.499  1.0
  Fe  Fe21  1  0.879  0.630  0.501  1.0
  Fe  Fe22  1  0.630  0.879  0.001  1.0
  Fe  Fe23  1  0.879  0.630  0.999  1.0
  Fe  Fe24  1  0.370  0.121  0.501  1.0
  Fe  Fe25  1  0.121  0.370  0.499  1.0
  Fe  Fe26  1  0.370  0.121  0.999  1.0
  Fe  Fe27  1  0.121  0.370  0.001  1.0
  Sn  Sn28  1  0.769  0.231  0.250  1.0
  Sn  Sn29  1  0.231  0.769  0.750  1.0
  Sn  Sn30  1  0.273  0.727  0.250  1.0
  Sn  Sn31  1  0.727  0.273  0.750  1.0
  Sn  Sn32  1  0.853  0.147  0.250  1.0
  Sn  Sn33  1  0.147  0.853  0.750  1.0
  Sn  Sn34  1  0.355  0.645  0.250  1.0
  Sn  Sn35  1  0.645  0.355  0.750  1.0
  Sn  Sn36  1  0.105  0.895  0.250  1.0
  Sn  Sn37  1  0.895  0.105  0.750  1.0
  Sn  Sn38  1  0.604  0.396  0.250  1.0
  Sn  Sn39  1  0.396  0.604  0.750  1.0
  Sn  Sn40  1  0.521  0.479  0.250  1.0
  Sn  Sn41  1  0.479  0.521  0.750  1.0
  Sn  Sn42  1  0.021  0.979  0.250  1.0
  Sn  Sn43  1  0.979  0.021  0.750  1.0
  Sn  Sn44  1  0.850  0.476  0.250  1.0
  Sn  Sn45  1  0.476  0.850  0.750  1.0
  Sn  Sn46  1  0.150  0.524  0.750  1.0
  Sn  Sn47  1  0.524  0.150  0.250  1.0
  Sn  Sn48  1  0.601  0.725  0.250  1.0
  Sn  Sn49  1  0.725  0.601  0.750  1.0
  Sn  Sn50  1  0.399  0.275  0.750  1.0
  Sn  Sn51  1  0.275  0.399  0.250  1.0
[/CIF]
.
The material described by ErFe6Sn6 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Fe(1), four equivalent Fe(3), four equivalent Fe(5), one Sn(2), one Sn(5), two equivalent Sn(1), two equivalent Sn(3), and two equivalent Sn(9) atoms to form distorted ErFe12Sn8 hexagonal bipyramids that share corners with four equivalent Er(1)Fe12Sn8 hexagonal bipyramids, faces with two equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, faces with two equivalent Er(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the second Er site, Er(2) is bonded to four equivalent Fe(2), four equivalent Fe(4), four equivalent Fe(5), one Sn(3), two equivalent Sn(10), two equivalent Sn(5), and three equivalent Sn(8) atoms to form distorted ErFe12Sn8 hexagonal bipyramids that share faces with six equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with two equivalent Er(1)Fe12Sn8 hexagonal bipyramids, and faces with four equivalent Er(2)Fe12Sn8 hexagonal bipyramids. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(9) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Er2Fe4Sn6 cuboctahedra, and faces with four equivalent Er(1)Fe12Sn8 hexagonal bipyramids. In the second Fe site, Fe(2) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(4), two equivalent Sn(10), two equivalent Sn(7), and two equivalent Sn(8) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with three equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, and faces with four equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(5), one Sn(1), one Sn(2), one Sn(3), one Sn(4), and two equivalent Sn(9) atoms. In the fourth Fe site, Fe(4) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(5), one Sn(5), one Sn(6), one Sn(7), one Sn(8), and two equivalent Sn(10) atoms to form distorted FeEr2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(4)Er2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Er2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(4)Er2Fe4Sn6 cuboctahedra,  a faceface with one Fe(4)Er2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Er2Fe4Sn6 cuboctahedra,  a faceface with one Er(1)Fe12Sn8 hexagonal bipyramid, and faces with three equivalent Er(2)Fe12Sn8 hexagonal bipyramids. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(3), one Fe(4), two equivalent Fe(5), one Sn(10), one Sn(3), one Sn(4), one Sn(5), one Sn(6), and one Sn(9) atom. There are ten inequivalent Sn sites. In the first Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Er(1), two equivalent Er(2), two equivalent Fe(4), and four equivalent Fe(5) atoms. In the second Sn site, Sn(6) is bonded in a 6-coordinate geometry to two equivalent Fe(4) and four equivalent Fe(5) atoms. In the third Sn site, Sn(2) is bonded in a 7-coordinate geometry to one Er(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the fourth Sn site, Sn(7) is bonded in a 6-coordinate geometry to two equivalent Fe(4) and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(8) is bonded in a 9-coordinate geometry to three equivalent Er(2), two equivalent Fe(4), and four equivalent Fe(2) atoms. In the sixth Sn site, Sn(9) is bonded in a 8-coordinate geometry to one Er(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), and one Sn(9) atom. In the seventh Sn site, Sn(10) is bonded in a 8-coordinate geometry to one Er(2), two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(5), and one Sn(10) atom. In the eighth Sn site, Sn(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the ninth Sn site, Sn(3) is bonded in a 9-coordinate geometry to one Er(2), two equivalent Er(1), two equivalent Fe(3), and four equivalent Fe(5) atoms. In the tenth Sn site, Sn(4) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(5) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er(FeSn)6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   19.204
_cell_length_b   19.204
_cell_length_c   5.416
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   153.035
_symmetry_Int_Tables_number   1
_cell_volume   905.725
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Er  Er0  1  0.190  0.810  0.250  1.0
  Er  Er1  1  0.810  0.190  0.750  1.0
  Er  Er2  1  0.937  0.063  0.250  1.0
  Er  Er3  1  0.063  0.937  0.750  1.0
  Fe  Fe4  1  0.500  0.000  0.500  1.0
  Fe  Fe5  1  0.000  0.500  0.500  1.0
  Fe  Fe6  1  0.500  0.000  0.000  1.0
  Fe  Fe7  1  0.000  0.500  0.000  1.0
  Fe  Fe8  1  0.754  0.754  0.500  1.0
  Fe  Fe9  1  0.754  0.754  0.000  1.0
  Fe  Fe10  1  0.246  0.246  0.500  1.0
  Fe  Fe11  1  0.246  0.246  0.000  1.0
  Fe  Fe12  1  0.565  0.940  0.250  1.0
  Fe  Fe13  1  0.940  0.565  0.750  1.0
  Fe  Fe14  1  0.435  0.060  0.750  1.0
  Fe  Fe15  1  0.060  0.435  0.250  1.0
  Fe  Fe16  1  0.308  0.183  0.250  1.0
  Fe  Fe17  1  0.183  0.308  0.750  1.0
  Fe  Fe18  1  0.692  0.817  0.750  1.0
  Fe  Fe19  1  0.817  0.692  0.250  1.0
  Fe  Fe20  1  0.630  0.879  0.499  1.0
  Fe  Fe21  1  0.879  0.630  0.501  1.0
  Fe  Fe22  1  0.630  0.879  0.001  1.0
  Fe  Fe23  1  0.879  0.630  0.999  1.0
  Fe  Fe24  1  0.370  0.121  0.501  1.0
  Fe  Fe25  1  0.121  0.370  0.499  1.0
  Fe  Fe26  1  0.370  0.121  0.999  1.0
  Fe  Fe27  1  0.121  0.370  0.001  1.0
  Sn  Sn28  1  0.769  0.231  0.250  1.0
  Sn  Sn29  1  0.231  0.769  0.750  1.0
  Sn  Sn30  1  0.273  0.727  0.250  1.0
  Sn  Sn31  1  0.727  0.273  0.750  1.0
  Sn  Sn32  1  0.853  0.147  0.250  1.0
  Sn  Sn33  1  0.147  0.853  0.750  1.0
  Sn  Sn34  1  0.355  0.645  0.250  1.0
  Sn  Sn35  1  0.645  0.355  0.750  1.0
  Sn  Sn36  1  0.105  0.895  0.250  1.0
  Sn  Sn37  1  0.895  0.105  0.750  1.0
  Sn  Sn38  1  0.604  0.396  0.250  1.0
  Sn  Sn39  1  0.396  0.604  0.750  1.0
  Sn  Sn40  1  0.521  0.479  0.250  1.0
  Sn  Sn41  1  0.479  0.521  0.750  1.0
  Sn  Sn42  1  0.021  0.979  0.250  1.0
  Sn  Sn43  1  0.979  0.021  0.750  1.0
  Sn  Sn44  1  0.850  0.476  0.250  1.0
  Sn  Sn45  1  0.476  0.850  0.750  1.0
  Sn  Sn46  1  0.150  0.524  0.750  1.0
  Sn  Sn47  1  0.524  0.150  0.250  1.0
  Sn  Sn48  1  0.601  0.725  0.250  1.0
  Sn  Sn49  1  0.725  0.601  0.750  1.0
  Sn  Sn50  1  0.399  0.275  0.750  1.0
  Sn  Sn51  1  0.275  0.399  0.250  1.0
[/CIF]
.