The atomic structure of thin iron silicide film, grown epitaxially on the Si(111) surface, has been analyzed by means of the three-dimensional RHEED Patterson function analysis. The iron-silicide-terminated surface with (2 × 2) periodicity has been prepared by a solidphase epitaxy method. 2 ML of Fe were deposited on the Si(111)-(7 × 7) surface and annealed at 500 • C. Three-dimensional Patterson function was calculated from series of φ-scanned RHEED intensity distributions converted to the k-space. The resulting model of γ-FeSi2 structure consists of two silicide layers faulted to each other with three relaxed Si adatoms above the H3 site.PACS : 61.14.Hg, 68.55.-a