Abstract A systematic study was performed of the solid state reaction between a 100nm thick layer of a rare earth metal and a Si substrate. The solid state reaction of five different rare earth metals (yttrium, gadolinium, dysprosium, erbium and ytterbium) were studied by in situ X-ray diffraction measurements on Si(100), Si(111) and poly-Si. This allowed us to make a comparison between the different systems. The formation temperature of h-RESi1.7 are the highest on Si(111) and the lowest on poly-Si for all examined RE metals. Additionally, the texture of the Gd disilicide phase on Si(100) and Si(111) was investigated by means of ex situ pole figure measurements. The epitaxial relationship of hexagonal GdSi1.7 and orthorhombic GdSi2 on the different Si substrates is determined. The epitaxial growth is the strongest on Si(111).