The growth of single-crystal epitaxial CaSi2films on Si(111) is described along with a determination of the silicide atomic structure. Films were prepared using standard ultrahigh vacuum evaporation techniques in a silicon molecular beam epitaxy system. Cross-sectional transmission electron micrographs of atomically abrupt step-free interfaces extending well over 500 A are presented. These films constitute the first example of an epitaxial non-transition-metal silicide. The lack of d electrons and the large difference in electronegativity between Ca and Si provide a new single-crystal metal/silicon interface with significantly different characteristics from the thoroughly studied transition-metal silicides. © 1988, American Vacuum Society. All rights reserved.