Evidence of mixed valence states in UM2Al3 (M = Ni, Pd) studied by X-ray photoemission spectroscopy

Abstract We have measured the XPS valence band and core-level spectra of U M 2 Al 3 ( M = Ni and Pd). The results are compared with those of reference materials, dilute alloy U 0.1 La 0.9 Pd 2 Al 3 and itinerant 5 f compound URh 3 . The similarity of the core-level spectra between UPd 2 Al 3 and U 0.1 La 0.9 Pd 2 Al 3 suggests that their core-level spectra are governed by the interaction between U 5 f and ligand states of neighboring palladium and aluminum sites, with negligible contributions from neighboring uranium states. A complex satellite structure, observed in the core-level spectra of U M 2 Al 3 , suggests that the uranium atoms are in the strong mixed valence states with 5 f 2 (U 4+ ) and 5 f 3 (U 3+ ).