Electrons are affected by two thermodynamic forces [from the charge, ∇(E F / e c) where E F is the Fermi level and e c is the electron charge and temperature gradient, ∇(1/ T)] because they carry both charge and thermal energy, and thus electric current j e and heat flow q are described with the thermoelectric tensors (A ee, A et, A te, and A tt) from the Onsager reciprocal relations as j e = A e e ⋅ ⋅ ∇ ∇ E F e c + A e t ⋅ ⋅ ∇ ∇ 1 T , and q = A t e ⋅ ⋅ ∇ ∇ E F e c + A t t ⋅ ⋅ ∇ ∇ 1 T .