Surprising transport phenomena in magnets

I will describe two examples of particularly striking transport phenomena in interacting magnetic materials. They both reveal the major role played by interactions in uncovering novel phenomena. The first example will be an analysis of recent experiments in which a half-quantized thermal Hall conductivity in the in-field quantum spin liquid (Ising anyon phase) candidate \alpha-RuCl3. I will demonstrate that, surprisingly, the quantization of \kappa_H appears only in the presence of strong enough electron-phonon scattering. The second part of my presentation will be about the discovery of a singular signal (less than 1-degree wide) in the angular magnetoresistance in the magnetic Weyl semimetal CeAlGe, and its interpretation in terms of spontaneous symmetry breaking in this strongly spin-orbit coupled system. While this is the first such observation of this phenomenon, it will be clear that it should in fact occur quite generally in small Fermi surface spin-orbit coupled systems.