  Recent theoretical efforts predicted a type of unconventional antiferromagnet
characterized by the crystal symmetry C (rotation or mirror), which connects
antiferromagnetic sublattices in real space and simultaneously couples spin and
momentum in reciprocal space. This results in a unique C-paired spin-valley
locking (SVL) and corresponding novel properties such as piezomagnetism and
noncollinear spin current even without spin-orbit coupling. However, the
unconventional antiferromagnets reported thus far are not layered materials,
limiting their potential in spintronic applications. Additionally, they do not
meet the necessary symmetry requirements for nonrelativistic spin current.
Here, we report the realization of C-paired SVL in a layered room-temperature
antiferromagnetic compound, Rb1-{\delta}V2Te2O. Spin resolved photoemission
measurements directly demonstrate the opposite spin splitting between C-paired
valleys. Quasi-particle interference patterns reveal the suppression of
inter-valley scattering due to the spin selection rules, as a direct
consequence of C-paired SVL. All these experiments are well consistent with the
results obtained from first-principles calculations. Our observations represent
the first realization of layered antiferromagnets with C-paired SVL, enabling
both the advantages of layered materials and possible control through crystal
symmetry manipulation. These results hold significant promise and broad
implications for advancements in magnetism, electronics, and information
technology.
