Photoemission spectra for semiconducting SmS and metallic ${\mathrm{Sm}}_{0.5}$${\mathrm{Y}}_{0.5}$S give evidence of strong configuration interaction of localized states near the Fermi level involved in semiconductor-to-metal phase transitions and in unusual transport and magnetic properties. An analysis of the observed multiplet structure in photoemission spectra for semiconducting SmS shows a localized state of a mixed $f^6+f^{5}d$ character.

• Received 18 March 1974

DOI:https://doi.org/10.1103/PhysRevLett.33.161