Crossover of 5 character in -US, a Mott insulator with a narrow - hybridization gap

Metoki, Naoto   ; Sakai, Hironori   ; Suzuki, Michito; Yamamoto, Etsuji  ; Haga, Yoshinori   ; Matsuda, Tatsuma; Ikeda, Shugo*

It is revealed that the localized 5 state is stable at low temperature in US from the observation of crystal-field excitation. The crystal field excitation is strongly dumped and a magnetic quasi-elastic scattering is observed with decrease of the electrical resistivity in the order of 10 above 100 K. This is understood with the crossover of 5 electrons from the localized to the itinerant character. The band calculation by Suzuki . reported that US is a Mott insulator with a small - hybridization gap in the vicinity of the point. Therefore the crossover of 5 character is considered to be due to the hybridization effect, although the presence of the impurity level can not be ruled out experimentally.