Synthesis and thermal stability of topological semimetal R MnSb ₂ ( R = Yb, Sr, Ba, Eu)

YbMnSb2, a topological semimetal with an exotic band structure, has recently been found to exhibit potential thermoelectric transport properties in its single-crystalline formality. The fabrication of polycrystals, which have the advantages of easy synthesis and doping tunability, will advance the transport studies of YbMnSb2 but face challenges. Here, we found that the polycrystalline YbMnSb2, synthesized using the conventional melting method, unexpectedly exhibits obvious impurities due to the competing phase YbMn2Sb2. To avoid the high-temperature synthesis, high-quality polycrystalline bulk YbMnSb2, as well as three other RMnSb2 (R = Sr, Ba, Eu), were successfully prepared by mechanical alloying followed by spark plasma sintering. Based on the high-quality polycrystalline samples, it was discovered that YbMnSb2 reacts with oxygen during heating in the presence of small amounts of oxygen, resulting in MnSb, Yb2O3, and Sb. A similar oxidation phenomenon also occurs for the other RMnSb2. This work provides a feasible method for synthesizing high-quality RMnSb2 polycrystals, which should also be suitable for the other isostructural topological semimetals, paving the way for future studies of their transport properties.