High quality single crystal (0 0 1) Sm films and (0 0 1) Sm/Nd superlattices have been prepared by molecular beam epitaxy. The epitaxial growth is controlled by in situ RHEED measurement and the crystallographic structure is determined ex situ from large angle X-ray scattering. We show how the crystal structure of several-thousands-anstroms-thick samarium films can be tailored by the elaboration conditions (i.e. the deposition of a thin Nd template layer): either a nine hexagonal close-packed plane stacking sequence ("Sm-structure"), as bulk samarium, or a four hexagonal close-packed plane (dhcp) structure are obtained. Moreover, this unusual dhcp structure for pure samarium has also been stabilized in nanoscale (0 0 1) Sm/Nd superlattices that thus present a coherent dhcp stacking over several bilayers. Both dhcp Sm films and coherent dhcp Sm/Nd superlattices are of broad interest for investigations of the link between structure and magnetism in rare earth epitaxied systems. (C) 2002 Elsevier Science B.V. All rights reserved.