X-ray photoemission spectrum, electronic structure, and magnetism of UCuxSb2

•Electronic structure of UCuxSb2 probed by X-ray photoemission (XPS) and ab initio.•Good agreement between experimental and calculated (x = 0.75) XPS valence spectra.•Good accord between experimental and calculated ferromagnetic moments on U atoms.•Complex experimental core-level XPS spectrum with three: 1-, 3- and 7-eV satellites.•Concluded dual and mixed-valence configuration of U 5f states in UCu0.83Sb2.

The room temperature valence and core-level X-ray photoemission spectra of an UCu0.83Sb2 single crystal were measured using the Al Kα source. The related theoretical valence spectra were determined from densities of states for UCuxSb2 systems obtained from our band structure calculations using the FLAPW method in the LDA + U approximation, as implemented in the Wien2k code, and the supercell approach to simulate a deficit of the Cu atoms. The calculated spectrum of the Cu-deficit UCu0.75Sb2 is in good accord with the experimental one, revealing a complete localization of the Cu 3d electrons and a dual (both localized and itinerant) behavior as well as unusual spin-up polarization of the U 5f states near the Fermi level. Our calculated total magnetic moments on the uranium atom are in reasonable agreement with the experimental value of magnetization. Some localization and valence-mixing of the 5f-electrons are reflected by the triple-satellite (sats. 1-eV, 3-eV and 7-eV) structure, visible in the spectrum of the U 4f core-lines. Also the calculated Fermi surface of the stoichiometric system is complex, containing five spin-polarized sheets of different dimensionality with some nesting features.