Local symmetry breaking activates a forbidden anomalous Hall response in the kagome Weyl semimetal Mn₃Sn

Symmetry breaking at the local scale can fundamentally reshape the topological responses of quantum materials. In the kagome antiferromagnet Mn₃Sn, we combine neutron and synchrotron total scattering with magnetotransport to reveal an intrinsic short-range symmetry-breaking distortion that activates a symmetry-forbidden anomalous Hall response. Measurements on nearly stoichiometric Mn_3.002Sn show a finite anomalous Hall conductivity σ_xy emerging below the onset of inverse-triangular magnetic order (T_N1 ≈ 440 K) and persisting through a subsequent transition to an incommensurate helical phase with multiple k-vectors (T_N2 ≈ 280 K). While powder and single-crystal x-ray and neutron diffraction confirm a globally hexagonal P6₃/mmc symmetry across both transitions, total scattering and reverse Monte Carlo modeling reveal intrinsic short-range symmetry-breaking distortions that lift the macroscopic symmetry constraints. Our results directly link short-range correlations to the microscopic origin of the forbidden Hall response, establishing local symmetry breaking as a key mechanism for generating Berry-curvature–driven phenomena in kagome magnets.