Nature Communications, Published online: 20 June 2026; doi:10.1038/s41467-026-74634-4 It is possible to realize axion electrodynamics in a material with an isotropic and linear magnetoelectric response, however, such a material has thus far evaded experimental realization. Here, Mishra et al succeed in creating such a linear isotropic magnetoelectric response in powdered Chromia.