Soft x-ray angle resolved photoelectron spectroscopy study of heavy fermion superconductor UPd2Al3

We have performed angle-resolved photoemission experiments in soft X-ray region (SX-ARPES) for the heavy Fermion superconductor UPd2Al3 to observe its band structure. At low temperatures (20 K), renormalized quasi-particle bands were observed in the vicinity of the Fermi level. The overall structure of ARPES spectra including strongly dispersive bands on the higher binding energy sides is fairly well explained by the band structure calculation treating U 5f electrons as being itinerant. This suggests that itinerant description is a reasonable approach to understand their electronic properties at low temperatures. On the other hand, at high temperature (100 K), the quasi-particle bands moved toward higher binding energies, and became less dispersive. This suggests that the U 5f electrons change their character from itinerant one at low temperatures to localized one at high temperatures. These results give important information for the understanding of the unconventional superconductivity in this compound. (author)