Magnetism-Induced Breakdown of the Wiedemann–Franz Law in Kagome Metals

Magnetic Kagome metals host strongly coupled itinerant electrons and local magnetic moments, producing unconventional charge and heat transport. We present magnetization, electrical, and thermal measurements on a Cr-based Kagome compound showing a ferrimagnetic ground state with a transition near 10 K and a critical field of about 0.4 T. The electrical resistivity and Hall conductivity confirm metallic character with reduced spin-disorder scattering under field, whereas the transverse thermal conductivity displays a pronounced nonlinearity near the transition, indicating distinct regimes of heat-carrying excitations. Joint analysis of electrical and thermal conductivities reveals a breakdown of the Wiedemann–Franz law in the ordered phase and recovery of fermionic heat carriers above 4 K.