We have performed high-resolution Ce $3d-4f$ resonance photoemission (RPES) measurements for low Kondo temperature ${(T}_K)$ $\mathrm{Ce}\mathrm{MX}$ $(M=\mathrm{P}\mathrm{d},\mathrm{P}\mathrm{t},X=\mathrm{P},\mathrm{A}\mathrm{s},\mathrm{S}\mathrm{b})$ and compared the results with $4d-4f$ RPES. The experimental results reveal that the bulk Ce $4f$ electronic structures are remarkably different from those in the surface layer even in low-$T_K$ materials. The non-$4f$ valence-band spectra are well described by the results of the band-structure calculation of isostructural $\mathrm{La}\mathrm{MX}$ by considering the photoionization cross sections. We have analyzed the Ce $4f$ spectra by using a noncrossing approximation calculation based on the single-impurity Anderson model. The calculated results successfully reproduce the experimental $4f$ spectra. We find that the bare $4f$ level shift is the most important factor in explaining the difference between the surface and bulk Ce $4f$ spectra. Moreover, the Ce $4f$ states of $\mathrm{Ce}\mathrm{MX}$ are found to hybridize preferentially with a particular part of the p-d mixed antibonding states.

• Received 22 March 2001

DOI:https://doi.org/10.1103/PhysRevB.65.195109