Photoemission and x-ray absorption study of MgC_(1-x)Ni_3
  We investigated electronic structure of MgC_(1-x)Ni_3 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 E_F. However, we find that the sharp vHs peak theoretically predicted near the E_F is substantially suppressed. As for the Ni core level and absorption spectrum, there exist the satellites of Ni 2p 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 3d electrons may be important to understand various physical properties. 
J.H. Kim, J.S. Ahn, Jinsoo Kim, Min-Seok Park, S.I. Lee, E.J. Choi,   and S.-J. Oh