HIGH-RESOLUTION PHOTOEMISSION-STUDY OF UNI2AL3 AND URU2SI2

High-resolution low-temperature photoemission spectroscopy was perform ed for UNi2Al3 and URu2Si2 to study the nature of 5f electrons in U-ba sed heavy fermion materials. Photoemission spectra of both compounds h ave a sharp peak at EF and a large broad peak around 2 eV, while only UNi2Al3 exhibits an additional small broad feature at 0.6 eV. The two features in the vicinity of EF (the EF-peak and the small structure at 0.6 eV) were found to have a dominant U 5f character Comparison with the band structure calculations and experimental results on UPd2Al3 su ggests that the EF-peak is ascribed to itinerant U 5f electrons while the following broad feature at 0.6 eV represents localized f electrons .