Geometry-driven polar antiferromagnetic metallicity in a double-layered perovskite cobaltate

The coexistence of structural polarity and magnetism within a single material can give rise to coupled electromagnetic states, such as those observed in multiferroics. Unlike widely studied insulating polar materials, polar magnetic metals host unique coupling among their symmetry-breaking lattice distortions, spin order and intrinsic conductivity, offering a unique platform for emergent magnetotransport phenomena. Here we report a polar antiferromagnetic metallic state in the double-layered Ruddlesden–Popper perovskite Sr₃Co₂O₇. The cobalt ions at different sublayers develop inequivalent ionic displacements, geometrically generating a polar state while preserving metallic conductivity. Furthermore, the quasi-two-dimensional crystalline architecture hosts an A-type antiferromagnetic order with the Néel vector along the c axis, stabilized by interlayer hybridization of Co-d orbitals. Strikingly, despite negligible remanent magnetization, we observe a notable zero-field anomalous Hall conductivity, ascribed to the coupling between antiferromagnetism and polarity. This work highlights the pivotal role of symmetry engineering and geometric distortion in layered perovskites for designing multifunctional quantum materials.