Metallic p-wave magnet with commensurate spin helix

Antiferromagnetic states with a spin-split electronic structure exhibit spintronic responses despite nearly zero net magnetization. Recent theory has proposed p-wave magnets with the simplest odd-parity spin splitting based on the spin space group (arXiv:2309.01607). We report the experimental realization of a metallic p-wave magnet in a rare-earth-based helical magnet. By tuning the band filling of the helical magnet with a dominant Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction, we realize a coplanar spin-helical texture whose magnetic period is an even multiple of the crystal unit cell, as revealed by X-ray and neutron scattering. This magnetic structure breaks space-inversion symmetry; however, it preserves time-reversal plus a half-unit-cell translation symmetry, fulfilling the symmetry conditions for p-wave magnetism. Consistent with the anisotropic spin splitting, our p-wave magnet exhibits characteristic anisotropy in electronic conductivity. Relativistic spin–orbit coupling and a tiny spontaneous net magnetization further break time-reversal symmetry, resulting in a giant anomalous Hall effect with a Hall angle larger than 3% for an antiferromagnet.