Enhanced two-dimensional ferromagnetism in van der Waals β-UTe3 monolayers.

The discovery of local-moment magnetism in van der Waals (vdW) semiconductors down to the single-layer limit has led to a paradigm shift in the understanding of two-dimensional (2D) magnets. The incorporation of strong electronic and magnetic correlations in 2D vdW metals remains a sought-after platform to enable control of emergent quantum phases and to achieve more theoretically tractable microscopic models of complex materials. To date, however, there is limited success in the discovery of such metallic vdW platforms, and f-electron monolayers remain out of reach. Here, we demonstrate that strongly correlated β-uranium tritelluride (β-UTe3) can be exfoliated to the monolayer limit. Unexpectedly, β-UTe3 remains ferromagnetic in this limit with an enhanced ordering temperature of 35 kelvin, a factor of two larger than its bulk counterpart. Our work establishes β-UTe3 as a materials platform for investigating and modeling correlated behavior in the monolayer limit and opens numerous avenues for quantum control with, e.g., strain engineering.