While the thermoelectric performance of orthorhombic SnS and SnSe is well characterised, the IV-VI chalcogenides display a rich structural chemistry, with several potential phases that could show superior low-temperature thermoelectric performance (Figure ). Among these, the recently-discovered metastable cubic "π" phase of SnS and SnSe has shown considerable potential for photovoltaic applications. A recent study of the IV-VI chalcogenides also revealed new structural-property relationships that suggest the π structure should lend itself to low ) and rocksalt (Fm 3m) phases. These images were prepared using VESTA. κ latt . The potential thermoelectric performance of the π phases has been explored in several computational studies, but significant approximations in the calculations mean these results are at best indicative.