
Given the following passage

"An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of metallic phases (two or more solutions). Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types (see also: Van Arkel-Ketelaar triangle for information on classifying bonding in binary compounds).",

answer the following question. Note that the answer is present within the text.

Question: Which of the following is not a characteristic of intermetallic compounds: defined stoichiometry, bond types, or crystal structure? 

bond types
