High-resolution angle-resolved photoemission study of USb: Dual character of 5f electrons

We have performed a high-resolution angle-resolved photoemission spectrosco py (ARPES) on antiferromagnetic USb to study the electronic structure near the Fermi level. We found that USb has a metallic band structure with the f ully occupied Sb 5p bands in contrast to semimetallic CeSb that has the par tially filled Sb 5p bands. This suggests that the magnetic phase transition of USb is not understood within the framework of the p-f mixing model. Thi s difference in the electronic structure between USb and CeSb is ascribed t o the energy position of the respective bare f level with respect to the Sb 5p band. The observed fully occupied Sb 5p bands in USb is consistent with the band calculation based on the itinerant U 5f model, but different from that of the localized model. On the other hand, we found two dispersionles s bands just below E-F in ARPES spectra of USb, which are well described in terms of the 5f(2)-final-state multiplet structure calculated based on the localized 5f model. These experimental results suggest the dual (itinerant and localized) character of 5f electrons that characterizes anomalous prop erties of USb.