Ultraviolet photoemission study of single-crystal BaPb/sub 1/minus//ital x//Bi/sub /ital x//O/sub 3/

An ultraviolet photoemission study on single-crystal BaPb/sub 1/minus//ital x//Bi/sub /ital x//O/sub 3/ with/ital x/=0.15 (superconductor) and /ital x/=1.0 (semiconductor) has been presented. A clear Fermi-edge structure was observed for the first time for the superconducting compound. A rigid shift of the valence band by 0.3--0.4 eV between the superconductor and the semiconductor was observed although the shift is much smaller than predicted from the band-structure calculation. The ''mysterious 9-eV peak,'' whose origin has been controversial in cuprate superconductors, was found also for degraded crystal surfaces of BaPb/sub 1/minus//ital x//Bi/sub /ital x//O/sub 3/. Its origin was discussed in connection with the difference and similarity in the high-/ital T//sub /ital c// mechanism between cuprate and noncuprate superconductors.