An unconventional superconducting state was recently discovered in uranium ditelluride (UTe₂), in which spin-triplet superconductivity emerges from the paramagnetic normal state of a heavy-fermion material. The coexistence of magnetic fluctuations and superconductivity, together with the crystal structure of this material, suggests that a distinctive set of symmetries, magnetic properties, and topology underlie the superconducting state. Here, we report observations of a nonzero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together suggest that the superconductivity in UTe₂ is characterized by a two-component order parameter that breaks time-reversal symmetry. These data place constraints on the symmetries of the order parameter and inform the discussion on the presence of topological superconductivity in UTe₂.

最近在二碲化铀 (UTe ₂ ) 中发现了一种非常规的超导状态，其中自旋三重态超导性源自重费米子材料的顺磁常态。磁涨落和超导性的共存，以及这种材料的晶体结构，表明超导状态具有一组独特的对称性、磁性和拓扑结构。在这里，我们报告了对非零极性克尔效应和进入超导状态时比热的两个跃迁的观察结果，这些共同表明 UTe ₂中的超导性其特征在于打破时间反转对称性的两分量顺序参数。这些数据对有序参数的对称性施加了限制，并为关于 UTe _{2 中}存在拓扑超导性的讨论提供了信息。