Having verified our calculated bandgaps, the electronicstructure calculations were used as the basis for electronictransport calculations using semi-classical Boltzmann transport theory and an approximate model of the electron relaxation times. Within this framework, the electrical properties are calculated for a set of specified temperatures and extrinsic carrier concentrations n ("doping levels"). We selected a temperature range of 300 -900 K, with room temperature being the practical lower limit for thermoelectric applications and 900 K close to the reported phase-transition temperatures of the Pnma phases. A range of doping levels between n = 10 16 -10 20 cm -3 was chosen to bracket the intrinsic carrier concentration of 10 16 cm -3 reported for GeSe and the n ≈ 5 × 10 19 cm -3 reported in experiments on doped SnSe. Experiments on the Ge and Se chalcogenides typically target p-type (hole) doping, which is readily achieved in SnSe e.g. by substituting Sn with Ag or Na , or by promoting Sn vacancies. However, n-type (electron) doping has also been reported for both SnS and SnSe, and has been predicted to lead to favourable properties in Pnma GeS. We therefore considered both types of doping. We note that the n is set by adjusting the position of the Fermi energy E F in the electronic-structure calculations, and the calculations therefore do not consider the practicality or potential effect of incorporating the defects or dopants required to achieve a target doping level.