Pseudogap of Charge-Density-Wave Compound SmNiC2 Studied by High-Resolution Photoemission Spectroscopy

We have performed high-resolution photoemission spectroscopy of a rare-earth inter-metallic compound SmNiC2 which undergoes a charge-density-wave (CDW) transition at T-CDW 148 K and a ferromagnetic transition at T-C = 17.5 K. We have determined the valence-band and near-E-F (Fermi level) electronic states, and observed a marked suppression of the spectral density of states (DOS) within 60-70 meV with respect to E-F below T-CDW, indicative of a partial gap (pseudogap) opening due to the CDW formation. Finite DOS at E-F in the CDW state suggests an imperfect nature of the Fermi-surface nesting.