Observation of the amplified transverse thermoelectric signals by reduced-dimensionality transport anisotropy.

Transverse thermoelectric devices offer simplified geometries with flexible designs for next-generation cryogenic technologies. However, mechanisms on geometrical amplification of transverse thermoelectric effects remain elusive. Here we establish a general framework linking reduced dimensionality with its geometrical anisotropy to enhanced transverse thermoelectric responses. Taking quasi-one-dimensional Li0.9Mo6O17 as a model platform, we combine theoretical modeling with systematic experiments to reveal extraordinarily large Nernst and Ettingshausen signals, reaching 11,430 μV/K (25 K, 9 T) and 0.0063 K · m/A (43.1 K, 9 T), respectively, together with a high power factor of 814 μW cm-1 K-2 at 25 K and 9 T. Dimensional reduction amplifies the Seebeck-driven electric field and enhances the reduced mobility through anisotropic Fermi surface geometry. These effects yield the transverse thermoelectric response far exceeding those of higher-dimensional systems with even ultrahigh carrier mobilities. Our findings highlight enhanced geometrical anisotropy as a powerful principle of design for engineering high-performance transverse thermoelectric systems.