Experimental Fermi surface determination of epitaxial ErSi1.7(0001) on Si(111)

The Fermi surface of ErSi1.7(0001) thin films grown epitaxially on Si(111) has been measured by angular photoemission intensity distribution maps at different photon energies using synchrotron radiation. Valence-band spectra at different collection angles along the main symmetry directions of the surface Brillouin zone (SBZ) have been measured, and they have allowed us to find that the Fermi surface is characterized by hole and electron pockets at particular high-symmetry points of the SBZ. The shape of the experimental Fermi surface for different photon energies is similar, indicating a bidimensional electronic character, in contrary to the expectation based upon band-structure calculations and the crystallographic structure. Moreover, Si 2p core-level photoemission spectra taken at surface-sensitive conditions reveal only one chemical state for the Si atoms at the surface layer.