Effects of Ce-Lu substitution on thedvalence states of Laves phases

The legitimacy of the extraction procedure of the 4f spectral function for Ce intermetallic compounds by modeling the non-f states in terms of isostructural substitutions of the rare-earth species is analyzed by combined ultraviolet direct and inverse photoemission spectroscopy on ${\mathrm{CeCo}}_2$, ${\mathrm{LuCo}}_2$, ${\mathrm{CeRh}}_2$, and ${\mathrm{LuRh}}_2$. We find that the occupied states show a strong sensitivity to the R substitution when the R atoms interact strongly with the metal as in the extended 4d M wave functions (Rh) while the variations are negligible in the case of 3d M partner (Co). The more delocalized empty states are sensitive to the Ce-Lu substitution both in R${\mathrm{Co}}_2$ and R${\mathrm{Rh}}_2$ systems. The results are discussed in terms of the different spatial extent of Ce and Lu 5d wave functions and of the degree of intermixing with the M partner d valence states.