Band gap stability in CeRhSb

The electronic structure and magnetic properties of CeRhSb were investigated by substituting Rh with 10% of Pd or Co, or Sb with 10% Sn. The $3d$ and $4d$ x-ray photoelectron spectroscopy (XPS) spectra show that CeRhSb and its alloys with Pd and Co are mixed valent. For Sn, the spectra are consistent with trivalence. Analysis of the f² weight in the $3d$ XPS spectra using Gunnarsson-Sch\"onhammer theory suggests a hybridization constant of 140 meV for CeRhSb and about 170 meV for its alloys. Linearized muffin-tin orbital calculations give a pseudo-V-shape gap located at the Fermi level. This classifies these materials as semimetals rather than semiconductors. The location of the pseudogap in CeRhSb varies with the number of valence electrons. We discussed the correlation between the gap at the Fermi level and the number of free electrons, the valence of Ce, and the f-d hybridization.