Schulze in 1967 defined intermetallic compounds as solid phases containing two or more metallic elements, with optionally one or more non-metallic elements, whose crystal structure differs from that of the other constituents. Under this definition, the following are included:
# Electron (or Hume-Rothery) compounds
# Size packing phases. e.g. Laves phases, Frank–Kasper phases and Nowotny phases
# Zintl phases
The definition of a metal is taken to include:
# post-transition metals, i.e. aluminium, gallium, indium, thallium, tin, lead, and bismuth.
# metalloids, e.g. silicon, germanium, arsenic, antimony and tellurium.
Homogeneous and heterogeneous solid solutions of metals, and interstitial compounds such as the carbides and nitrides are excluded under this definition.  However, interstitial intermetallic compounds are included, as are alloys of intermetallic compounds with a metal.