Evidence of the Intrinsic Metallic Character of Some Rare-Earth Pnictides

From measurements of the low-temperature specific heat of bulk crystals of YSb and GdSb and photoemission spectra from a single crystal of GdSb we conclude that these compounds are intrinsic metals. The electronic contribution to the specific heat of YSb was found to be 0.9 mJ/mole deg2 which may be compared with 0.65 for Ag, a good metal. Photoemission spectra for GdSb show structure at the Fermi level EF which is consistent with an s-like band at EF which overlaps a ``valence band'' with a peak at 2.2 eV below EF. This band picture offers an alternative explanation for the absorption spectra which have been interpreted as evidence for a large bandgap in the rare-earth pnictides.