Osmium silicide epilayers have been grown by molecular beam epitaxy on (100)-oriented Si wafers. Multiple-phase (Os2Si3 and OsSi2) and single-phase epilayers are observed, depending on the growth parameters. In this paper we report on a detailed investigation of the structure of a single-phase Os2Si3 epilayer and epilayer/silicon interface using X-ray diffraction, and reflectivity analysis. Optical absorption results will also be presented. (c) 2006 Elsevier B.V. All rights reserved.