any of a class of substances composed of definite proportions of two or more elemental metals, rather than continuously variable proportions (as in solid solutions). The crystal structures and the properties of intermetallic compounds often differ markedly from those of their constituents. In addition to the normal valences of their components, the relative sizes of the atoms and the ratio of the total number of valence electrons to the total number of atoms have important effects on the composition of intermetallic compounds. See also alloy.