Semiconducting MnSi1.7, layers were grown on Si(1 1 1) substrates by reactive deposition epitaxy in the presence of an Sb flux. The defect microstructure and epitaxial relationship of the layers were examined by X-ray diffraction and transmission electron microscopy. It was found that epitaxial MnSi1.7 layers with continuous and relatively smooth interfaces could be grown. The predominant epitaxial relationship adopts the (3 3 2), [(1) over bar 1 0]MnSi(1.7subcell)parallel to (1 1 1), [(1) over bar 1 0]Si using MnSi1.7 subcell notation, even though various growth variants still remain in the layer. The secondary ion mass spectroscopy profile reveals Sb segregation at the interface between the silicide and Si substrate.