UNi4Mn: A non-centrosymmetric uranium intermetallic exhibiting room-temperature ferromagnetism

We report UNi 4 Mn, a non-centrosymmetric uranium intermetallic exhibiting room-temperature ferromagnetism with a Curie temperature (T C ) of 336 K. This behavior arises from localized Mn 2+ moments and enhanced 5 f -3 d hybridization. Differential thermal analysis indicates congruent formation at 1185 °C. The compound crystallizes in the cubic MgCu 4 Sn-type structure (Pearson symbol cF 24, space group F- 43 m ) with Mn atoms fully ordered on the 4 c site, as determined by X-ray and neutron diffraction. Magnetization measurements yield an effective magnetic moment (μ eff ) of 5.6 μ B per formula unit and a saturation magnetic moment (μ sat ) of 4.85 μ B per formula unit, consistent with localized Mn 2+ behavior. Neutron diffraction reveals magnetic moments only on the Mn sites, while U and Ni atoms remain nonmagnetic; Mn moments order ferromagnetically and align along the cubic face diagonal. Density functional theory calculations reproduce the ferromagnetic ground state of UNi 4 Mn and its Ce analogue CeNi 4 Mn, and confirm the Pauli-paramagnetic character of UNi 5 . The calculations further show that enhanced 5 f -3 d hybridization strengthens exchange interactions, leading to Dirac-like electronic features and a pseudogap at the Fermi level, with potential implications for spintronic and quantum devices. To our knowledge, UNi 4 Mn represents the first uranium-based intermetallic combining room-temperature ferromagnetism with non-centrosymmetric symmetry, providing mechanistic insight into how chemical ordering, hybridization, and local coordination govern magnetic exchange in actinide intermetallics.