Identifying altermagnets unambiguously in experiments remains a challenge. Tim Kokkeler of QMAT's Condensed Matter Theory group at the University of Jyväskylä, with Vitaly Golovach and Sebastian Bergeret in San Sebastián, has developed a theory of angle-dependent magnetoresistance in metallic altermagnets coupled to ferromagnetic insulators.

They show that the recently reported spin-splitter magnetoresistance differs qualitatively from the familiar spin Hall magnetoresistance in three ways: it depends only on the relative orientation of the magnetisation and the altermagnet's Néel vector, its longitudinal response has the opposite sign, and its longitudinal and transverse signals are directly proportional. Its full angular dependence would therefore be a smoking-gun signature of d-wave altermagnetism, and gives a recipe for finding the Néel vector from standard measurements.

The preprint has not yet been peer reviewed.

Figure: Kokkeler et al., arXiv:2605.10747 (2026), CC BY 4.0