Possible Kondo resonance in PrFe4P12 studied by bulk-sensitive   photoemission
  Pr 4f electronic states in Pr-based filled skutterudites PrT4X12(T=Fe and Ru; X=P and Sb) have been studied by high-resolution bulk-sensitive Pr 3d-4f resonance photoemission. A very strong spectral intensity is observed just below the Fermi level in the heavy-fermion system PrFe4P12. The increase of its intensity at lower temperatures is observed. We speculate that this is the Kondo resonance of Pr, the origin of which is attributed to the strong hybridization between the Pr 4f and the conduction electrons. 
A. Yamasaki, S. Imada, T. Nanba, A. Sekiyama, H. Sugawara, H. Sato, C.   Sekine, I. Shirotani, H. Harima, and S. Suga