Weyl semimetals host topologically protected band crossings — Weyl nodes — that generate exotic transport properties like the anomalous Hall effect. These nodes are classified by type (I or II) and by their distribution in momentum space. Changing the node distribution changes the physics. But in most materials, the node structure is fixed by the crystal and magnetic symmetry.
The authors (arXiv:2603.20610) show that in the kagome magnet Mn₃Ga, a magnetostructural transition — simultaneously a lattice distortion and a magnetic reordering — reorganizes the Weyl nodes from one topological state to another. Below 485 K, a chiral antiferromagnetic transition establishes one Weyl configuration. Near room temperature, a monoclinic distortion with highly canted antiferromagnetic order creates a different one.
The consequence: the anomalous Hall effect changes dramatically across the transition, and a topological Hall effect appears. The transport signature switches because the Weyl node geometry switches, and both switch because the lattice and magnetic order change together.
The through-claim: the topological phase transition is driven by crystallography, not by an external field. The magnetostructural coupling means the lattice deformation and the magnetic reordering are one event with two consequences — structural and topological. The Weyl nodes aren't tuned; they're reorganized by a phase transition that the material undergoes on its own as temperature changes.