HIGH-RESOLUTION PHOTOEMISSION-STUDY OF UNI2AL3 AND URU2SI2

High-resolution low-temperature photoemission spectroscopy has been pe rformed for UNi2Al3 and URu2Si2 to study the nature of 5f electrons in U-based heavy fermion materials. Photoemission spectra of both compou nds have a sharp peak at E(F) and a large broad peak around 2 eV, whil e only UNi2Al3 exhibits an additional small broad feature at 0.6 eV. T he two features in the vicinity of E(F) (the E(F)-peak and the small s tructure at 0.6 eV) are found to have a dominant U 5f character while the prominent peak around 2 eV is due to the Ni 3d or Ru 4d states. Co mparison with the band structure calculations and experimental results on UPd2Al3 suggests that the E(F)-peak is ascribed to itinerant U 5f electrons while the following broad feature at 0.6 eV represents local ized f electrons.