Transverse and Longitudinal Magnetothermopower Promoted by Ambipolar Effect in Half‐Heusler Topological Materials

Abstract Topologically trivial and non‐trivial semimetals with a high degree of carrier compensation are well known for demonstrating large transverse magnetothermopower ( S _yx ). However, in such systems, the longitudinal magnetothermopower ( S _xx ) is typically suppressed due to nearly perfect electron‐hole compensation. Here, it is shown that the half‐Heusler topological semimetal DyPtBi exhibits simultaneously large S _xx and S _yx magnetothermopowers, defying this conventional trade‐off. In B = 14 T, thermopower of DyPtBi reaches peak values of S _xx = 131 µV K ⁻¹ at T = 149 K and at T = 200 K, and transverse component remains significantly large even at 290 K (). Remarkably, at T = 290 K and in relatively weak magnetic field of 1 T, both relevant for practical applications, DyPtBi shows , which is one of the largest values reported under such conditions. The large transverse thermopower originates from an ambipolar effect associated with thermal excitation occurring in zero‐gap semiconductors. Due to the imperfect electron‐hole compensation, an intrinsic asymmetry between hole‐ and electron‐type carriers enables pronounced values of both S _xx and S _yx , resulting in high effective thermopower () in DyPtBi at 200 K. A comparative analysis with DyPdBi, another half‐Heusler material that demonstrates large but small (both values obtained at T = 293 K and B = 14 T), highlights the critical role of band structure and compensation tuning. These findings underscore the potential of chemical doping and band engineering in rare‐earth‐based half‐Heusler materials for optimizing both transverse and longitudinal thermoelectric properties.