Topological semimetals have attracted tremendous attention from the science community owing to their exotic electronic structures. It is generally assumed that metallic or similar systems exhibit rather poor thermoelectric performance due to very small Seebeck coefficients. Here we demonstrate by first-principles calculations and Boltzmann transport theory that the Dirac semimetal Na₂AgSb is an exception because of its strong band asymmetry around the Fermi level. In addition, the system shows ultralow lattice thermal conductivity caused by the rattling of the Na atoms in the cage-like framework of Ag and Sb atoms. As a consequence, one can realize certain decoupling of the thermoelectric transport coefficients, and a considerable ZT value of 1.3 can be reached at 300 K in the p-type Na₂AgSb. The present work highlights the promising possibility of semimetals or similar systems for high-performance thermoelectric applications.

拓扑半金属由于其奇异的电子结构而引起了科学界的极大关注。由于非常小的塞贝克系数，通常假设金属或类似系统表现出相当差的热电性能。在这里，我们通过第一性原理计算和玻尔兹曼输运理论证明，狄拉克半金属 Na ₂ AgSb 是一个例外，因为它在费米能级附近具有很强的带不对称性。此外，该系统显示出超低的晶格热导率，这是由 Ag 和 Sb 原子的笼状框架中的 Na 原子的颤动引起的。因此，可以实现热电传输系数的一定解耦，并且在 300 K 时可以达到相当可观的ZT值 1.3。p型Na ₂ AgSb。目前的工作突出了半金属或类似系统用于高性能热电应用的有希望的可能性。