The large predicted κ κ κ of the R3m phases means the predicted ZT max are not competitive with the Pnma structures, but p-type doping is nonetheless predicted to achieve ZT ≈ 1 between 650 -750 K, which is promising and which may be useful for some applications. Given that experimental work on alloys suggests it may be possible to mitigate the large κ κ κ latt and/or to enhance the electrical properties, we also suggest these materials may warrant further investigation.