The surface structure, interface reactivity, electron configuration and magnetic properties of Sm layers deposited on Si(001) at various temperatures are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magneto-optical Kerr effect (MOKE). It is found that metal Sm is present on samples prepared at low temperature, with an interface layer containing SmSi 2 and Sm 4 Si 3. When samples are prepared at high temperature, much less metal Sm is found, with an increasing amount of SmSi 2. Room temperature ferromagnetism is observed for all prepared layers, with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly a compound with approximate stoichiometry Sm 4 Si 3. Also, the decrease in the intensity of the XAS 2p 3/2 → 3d white lines with the corresponding increasing amount of SmSi 2 may be explained by assuming a higher occupancy of Sm 5d orbitals (5d 2 configuration), most probably due to hybridation effects.