(100) oriented metal alloy films containing both body‐centered cubic (bcc) and face‐centered cubic (fcc) metals have been deposited on (100) Si using Pd/Cu seed layers. These include FeCo, FePt, FePd, FeCu, FeAu, FeAg, FeNi, VNi, and CrNi with different compositions. All the alloys show (200) spacings close to those of either the bcc or fcc component metals. To compare with Vegard’s rule, a correction factor of (1.5)1/2is needed between the fcc and bcc lattices, with the fcc spacing being 22% larger. Twenty alloy spacings are compared, assuming that both the lattice structures and spacings of the alloy films are mainly determined by the component metals whose spacings are close to those of the alloys. Good agreements with the Vegard’s rule are obtained for the thirteen (100) alloys with lattice spacings close to those of their respective bcc component metals, and for the seven (100) alloy films with lattice spacings close to their fcc component metals.