${\mathrm{U}}_2\mathrm{N}{\mathrm{i}}_2\mathrm{Sn}$ is a member of a large family of intermetallic compounds with the tetragonal $\mathrm{M}{\mathrm{o}}_2\mathrm{Fe}{\mathrm{B}}_2$ crystal structure. It orders antiferromagnetically at 25 K with propagation vector $q=(0,0,\frac{1}{2})$. Magnetization, magnetoacoustic, and neutron-diffraction experiments on a single crystal provide evidence that the uranium moments align parallel to the $c$ axis with the anisotropy energy of ≈170 K, indicating that ${\mathrm{U}}_2\mathrm{N}{\mathrm{i}}_2\mathrm{Sn}$ can be classified as an Ising system. The results are at variance with previous studies on polycrystals, which indicated different magnetic structure, and which were incompatible with the $5f\text{−}5f$ two-ion anisotropy model dominant in most U band systems. High-field magnetization studies exhibit a weak linear response for fields along the basal plane up to the highest field applied (60 T), while the $c$-axis magnetization curve exhibits three metamagnetic transitions at approximately 30, 39, and 50 T. The U magnetic moments of $0.87{\mu }_{\mathrm{B}}$, the low magnetic entropy, and the enhanced Sommerfeld coefficient $\gamma =187\mathrm{mJ}/\mathrm{mol}\mathrm{f}.\mathrm{u}.{\mathrm{K}}^2$ suggest that ${\mathrm{U}}_2\mathrm{N}{\mathrm{i}}_2\mathrm{Sn}$ can be classified as an itinerant antiferromagnet with strong electron-electron correlations.

• Received 27 November 2018
• Revised 25 January 2019

DOI:https://doi.org/10.1103/PhysRevB.99.064415