Dual Character of 5f Electrons in UPd₂Al₃ Observed by High-Resolution Photoemission Spectroscopy

Comparative high-resolution temperature-dependent photoemission measurements were performed for UPd₂Al₃ and UPd₃. The photoemission spectrum near E_F of UPd₂Al₃ consists of a sharp peak at E_F and a broad band at 0.5-1.0 eV binding energy, both features having U 5f character. The sharp feature at E_F shows good agreement with a recent band structure calculation, while the broad band matches well with the U 5f-derived localized feature in UPd₃, indicating the dual character of 5f electrons in UPd₂Al₃. The intensity of the broad band relative to the E_F-peak increases with increasing temperature, suggesting that the localized character of 5f electrons in UPd₂Al₃ increases at higher temperatures. These observations are consistent with the transport and magnetic measurements which imply a temperature-dependent dual (itinerant and localized) character of U 5f electrons in UPd₂Al₃.