XANES study of rare-earth valency in LRu4P12 (L = Ce and Pr)

Valency of Ce and Pr in LRu4P12 (L=Ce and Pr) was studied by L-2,L-3-edge x -ray absorption near-edge structure: (XANES) spectroscopy. The Ce-L-3 XANES spectrum suggests that Ce is mainly trivalent, but the 4f state strongly h ybridizes with ligand orbitals. The band gap of CeRu4P12 seems to be formed by strong hybridization of 4f electrons. Pr-L-2 XANES spectra indicate tha t Pr exists in trivalent state over a wide range in temperature, 20 K less than or equal to T less than or equal to 300 K. We find that the metal-insu lator (MI) transition at T-MI = 60 K in PrRu4P12 does not originate from Pr valence fluctuation. [S0163-1829(99)01244-8].