A $5f$-like photoemission peak emerges at $E_F-0.78\mathrm{}$ eV in normal emission from UN(100) upon cooling below $T_{\mathrm{N}\acute{e}\mathrm{el}}=53\mathrm{}$ K. This is the first observation of its kind for $f$ electrons. We believe that this peak arises from band states which are folded back into the new antiferromagnetic Brillouin zone owing to the doubling of the unit cell along $〈100〉$. Isoelectronic USb, which has localized $5f$ electrons, does not exhibit such a temperature effect. Our results suggest that UN can be described within the theory of itinerant-$5f$-electron antiferromagnetism.

• Received 16 February 1983

DOI:https://doi.org/10.1103/PhysRevB.28.1490