Cooperative Goniopolar and Anomalous Nernst Transverse Thermoelectricity in Kagome Magnets

Transverse thermoelectrics (TEs), enabling interconversion between orthogonal heat and electric currents, offers unique advantages in device geometry and design flexibility. Yet, achieving large transverse TE signals at room temperature remains challenging. Here, we establish a cooperative framework in which the goniopolar effect and the anomalous Nernst effect jointly enhance the transverse TE response in kagome magnets. We demonstrate that kagome lattice-derived electronic structures intrinsically yield axis-dependent polar Seebeck coefficients arising from flat bands and van Hove singularities (VHSs), while broken time-reversal symmetry induces topological band splitting that generates large net Berry curvature within the same energy window. Combining transport measurements, DFT calculations and real-space thermal imaging, we demonstrate a room-temperature record cooperative transverse TE signal of 15.6 µV/K in the kagome ferromagnet MgMn₆Sn₆ among metallic systems. Our findings establish a cooperative framework linking the anomalous Nernst and goniopolar effects and provide a widely applicable design strategy for achieving large transverse TE response in kagome magnets.