Despite the challenges of stabilising and heavily doping the π phases, in our view the exceptional predicted TE performance, and in particular the ultra-low low-temperature κ latt , warrants further investigation. On the last point, this study evidences the successful strategy of targeting structural complexity as a route to achieving low room-temperature κ latt and high low-temperature ZT . If our understanding of the IV-VI chalcogenides generalises to the related group IV oxides and V-VI sesquioxides/sesquichalcogenides, further investigation of the low-symmetry orthorhombic phases of the Sb 2 Ch 3 and Bi 2 Ch 3 , or ternary IV-V oxides in the pyrochlore and derived structure types, 38 could be rewarding.