Solid phase epitaxy of amorphous SnxGe1-x films on strain relieved Ge films on Si(001) substrates was investigated for alloy compositions in the range 0.02 ≤x≤ 0.26. Films with compositions x < 0.05 crystallize by solid phase epitaxy as substitutional, strain relieved, diamond cubic alloys without phase separation or surface segregation of Sn. Films with higher Sn compositions exhibit more complicated behavior in which phase separation is believed to follow solid phase epitaxy. This sequence of transformations for higher Sn compositions yields epitaxial, substitutional, strain relieved, diamond cubic SnxGe1-x films with x ~ 0.05, and excess Sn is segregated in ~ 100 nm size domains within the epitaxial alloy film.