Abstract: Thermomagnetic refrigeration based on the Ettingshausen effect is a low-temperature solid-state cooling technology with advantages of precise temperature control, compact size, and noiseless operation. In recent years, topological semimetals, which possess both electrons and holes as charge carriers and exhibit high carrier mobility, have shown excellent thermomagnetic performance at low temperatures, making them promising candidates for cryogenic applications. In this study, highly dense polycrystalline TaSb₂ was synthesized via solid-state reaction followed by spark plasma sintering, and its low-temperature thermomagnetic transport properties were systematically investigated. The results show that the Nernst thermopower peaks at around 27 K and increases with applied magnetic field. Under 9 T and 26 K, the Nernst power factor reaches 315.1 μW·cm^-1·K^-2, while under 9 T and 22 K, the Nernst figure-of-merit is 7.1×10^-4 K^-1, both outperforming most reported polycrystalline thermomagnetic materials. Mechanistic analysis indicates that the high performance originates from the combined effects of strong bipolar effect, high carrier mobility, and significant phonon-drag enhancement of thermopower. Moreover, magnetic fields markedly suppress the electronic contribution to thermal conductivity at low temperatures, making the total thermal conductivity predominantly determined by the lattice component. This work offers a new material option and design strategy for low-temperature solid-state cooling applications. The relatively high lattice thermal conductivity partially limits the thermomagnetic performance, further reduction via phonon engineering could lead to substantial improvements.

Key words: topological semimetal, polycrystalline TaSb₂, thermomagnetic effect, bipolar effect, phonon drag