Structural phase transition and transport properties in topological material candidate NaZn₄As₃

We report a comprehensive study on a layered-structure compound of NaZn4As3, which has been predicted to be an ideal topological semimetal (TSM) candidate. It is found that NaZn4As3 undergoes a structural transformation from high temperature rhombohedral to a low temperature monoclinic phase. The electric resistivity exhibits a metal-to-insulator-like transition at around 100 K, and then develops a plateau at low temperature, which might be related to the protected topologically conducting surface states. Our first-principles calculation confirms further that NaZn4As3 is a topological insulator (TI) for both different phases rather than a previously proposed TSM. The Hall resistivity reveals that the hole carriers dominate the transport properties for the whole temperature range investigated. Furthermore, an obvious kink possibly associated to the structure transition has been detected in thermopower around ∼170 K. The large thermopower and moderate κ indicate that NaZn4As3 and /or its derivatives can provide a good platform for optimizing and studying the thermoelectric performance.