Electronic Structure of the Novel Filled Skutterudite PrPt₄Ge₁₂ Superconductor

We have performed soft x-ray photoemission spectroscopy (SXPES) and resonant photoemission spectroscopy (RPES) of the filled skutterudite superconductor PrPt₄Ge₁₂ in order to study the electronic structure of valence band and the character of Pr 4f. SXPES of PrPt₄Ge₁₂ measured with 1200 eV photon energy, where spectral contribution of Pr 4f is negligible, was found nearly identical with that of LaPt₄Ge₁₂, indicating similarity of Pt–Ge derived electronic states of the two compounds. Good correspondence with band calculations allows us to ascribe the dominant Ge 4p character of the density of states at the Fermi level (E_F). Pr 3d → 4f RPES shows that, although Pr 4f electrons in PrPt₄Ge₁₂ are not as strongly hybridized with conduction electrons near E_F as in PrFe4P12, there are finite Pr 4f contribution to the states near E_F in PrPt₄Ge₁₂. These PES results give the information of fundamental electronic structure for understanding the physical properties of the novel filled skutterudite superconductor PrPt₄Ge₁₂.