Electronic structure of superconducting UBe/sub 13/

We have studied the actinide superconductor UBe/sub 13/ with resonant photoemission using synchrotron radiation 30< or =h..nu..< or =120 eV. In agreement with the anomalously high ..gamma.. value of 1.1 J/mole K/sup 2/, we find a high density of 5f states at the Fermi level E/sub F/. Uranium 6d electrons are not present at E/sub F/ as can be derived from the zero intensity at E/sub F/ in the off-resonance spectrum. The close resemblance of this off-resonance curve to a photoemission spectrum of pure Be suggests that the hybridization of U 5f electrons with Be s,p electrons is small. Indeed, the UBe/sub 13/ photoemission curves look like a superposition of U and Be curves. By using photoemission results from UO/sub 2/ as a reference, we find that the valence-band emission contains about one 5f electron. The present results on UBe/sub 13/ are compared with those of CeCu/sub 2/Si/sub 2/, another member of the family of exotic superconductors.