Giant anomalous Hall and Nernst effects in a heavy fermion ferromagnet

The anomalous Hall and Nernst effects refer to the perpendicular voltage drop generated by a magnetic material's magnetization in response to an applied current and temperature gradient. These effects can be harnessed to determine the Berry curvature and hold potential for future applications in electronic devices and thermoelectric energy conversion. We investigate the anomalous Hall and Nernst effects in the heavy-fermion ferromagnet CeCrGe₃ and its non-4f analog ferromagnet LaCrGe₃. We find that CeCrGe₃ exhibits a giant anomalous Hall angle and an anomalous Nernst coefficient, reaching values as high as 33% and ∼10μVK^-1, respectively, among the largest reported for topological magnets. Based on electronic band-structure calculations, we identify a series of topological flat bands carrying strong Berry curvature with a pronounced Ce 4f orbital character in CeCrGe₃, which are absent in LaCrGe₃, highlighting the crucial role of Kondo flat bands in generating large anomalous transport responses. Furthermore, we identify a breakdown of the anomalous Hall scaling relation and the nonlinear anomalous Mott relation, which we attribute to the breaking of the topological Kondo flat bands at finite temperatures.