Antiferromagnetism and semimetallicity in EuSb₂

Antiferromagnetic topological insulators (AFM TIs) have recently attracted a lot of interest because the breaking of time-reversal symmetry gaps the topological surface state, which gives rise to exotic effects like the quantum anomalous Hall effect. This makes AFM TIs promising candidates for spintronics applications. Antiferromagnetic semimetals are the gapless counterparts of AFM TIs, and in contrast have received less attention. Here, we demonstrate that EuSb₂ is a member of this material class. Using high-quality single crystals, we investigate this state by means of transport, magnetization, and specific heat. Despite the antiferromagnetic order that develops below 26 K, a large magnetoresistance is found at low temperatures, indicative of a semimetal.  The robustness of the semimetallicity against magnetic order relates EuSb₂ to the analog non-magnetic semimetal CaSb₂. Supported by DFT calculations, we attribute the semimetallicity to the distorted Sb square-nets in both diantimonides. This is an important step towards a more comprehensive exploration of AFM topological semimetals.