Photoemission and x-ray absorption study of (formula presented)

We investigated electronic structure of (formula presented) with photoemission and x-ray absorption spectroscopy. Both results show that overall band structure is in reasonable agreement with band structure calculations including the existence of von Hove singularity (vHs) near (formula presented) However, we find that the sharp vHs peak theoretically predicted near the (formula presented) is substantially suppressed. As for the Ni core level and absorption spectrum, there exist the satellites of Ni (formula presented) which have a little larger energy separation and reduced intensity compared to the case of Ni-metal. These facts indicate that correlation effects among Ni (formula presented) electrons may be important to understand various physical properties.