We present x-ray magnetic circular dichroism (XMCD) measurements performed at the uranium $M_{4,5}$ edges of the heavy-fermion superconductors ${\mathrm{UBe}}_{13}$ and ${\mathrm{UPt}}_3.$ Unexpectedly, the dichroic signal at the $M_5$ edge exhibits a double-lobe structure, comprised of a positive and negative peak. Therefore, out of the eight metallic uranium compounds so far investigated by XMCD, five exhibit a single-lobe and three a double-lobe structure at the $M_5$ edge. The existence of this structure points to the importance of the influence of the hybridization, Coulomb and exchange, and crystal-field interactions. The observed line shape can be used to access the magnetic character of the $j=7/2\mathrm{}$ level of the empty $5f$ density of states.

• Received 12 May 1999

DOI:https://doi.org/10.1103/PhysRevB.60.10606