Crystal-symmetry-paired spin–valley locking in a layered room-temperature metallic altermagnet candidate

Previous theoretical efforts have predicted a type of unconventional antiferromagnet characterized by a crystal symmetry that connects antiferromagnetic sublattices in real space and simultaneously couples spin and momentum in reciprocal space. This results in a unique crystal-symmetry-paired spin–valley locking and related properties including piezomagnetism and non-collinear spin current even without spin–orbit coupling. However, most known unconventional antiferromagnets do not meet the necessary symmetry requirements for non-relativistic spin current, and this limits applications in spintronic devices. Here we demonstrate crystal-symmetry-paired spin–valley locking in a layered room-temperature antiferromagnetic compound, Rb_1−δV₂Te₂O. Spin-resolved photoemission measurements directly show the opposite spin splitting between crystal-symmetry-paired valleys. Quasi-particle interference patterns show the suppression of intervalley scattering due to the spin selection rules that are a direct consequence of the spin–valley locking. These results suggest that Rb_1−δV₂Te₂O is a potential room-temperature altermagnet candidate. Our observations highlight a methodology that enables both the advantages of layered materials and possible control through crystal symmetry manipulation for advancements in magnetism, electronics and information technology.