Resonant photoemission study ofUNi5−xCux

Valence-band spectra of the intermetallic compounds $\mathrm{U}{\mathrm{Ni}}_{5-x}{\mathrm{Cu}}_x$ ($x=0.0, 2.5, \mathrm{and} 5$) have been measured using synchrotron radiation in the energy range 10 to 130 eV. In all compounds the $5f$-derived valence-band density of states is pinned to the Fermi energy. In contrast to earlier work, no splitting of the U $5f$ emission due to different final-state $5f$ configurations is observed in U${\mathrm{Cu}}_5$. This points towards an itinerant description of the $5f$ electrons in these compounds. A decrease in the intensity of the Ni two-hole satellite is observed in going from Ni metal and U${\mathrm{Ni}}_5$ to U${\left({\mathrm{Ni}}_{0.5}{\mathrm{Cu}}_{0.5}\right)}_5$ which can be related to a filling of the Ni $d$ band. Furthermore, a shift of the Ni satellite energy by 1.3 eV towards higher binding energies occurs in U${\left({\mathrm{Ni}}_{0.5}{\mathrm{Cu}}_{0.5}\right)}_5$.