3dcore-level photoemission spectra of intermetallic Yb compounds

The Yb 3d core-level photoemission spectra of trivalent YbAs, mixed-valence ${\mathrm{YbAl}}_3$, and divalent ${\mathrm{YbPb}}_3$ were measured with a Si Kα x-ray source. Significant intensities of divalent peaks were observed even for trivalent YbAs and mixed-valence ${\mathrm{YbAl}}_3$. This is probably due to the divalent surface layers, which makes difficult the estimation of the 4f hybridization strength from the 3d core-level spectra. The 4d core-level and the 4f spectra are consistent with this interpretation.