CaCuP films close to the stoichiometric point have p-type conductivity, as verified by the sign of both the Hall and Seebeck coefficients (Figures and). † The exact value of the conductivity depends on stoichiometry (Figure ). The first trend is a conductivity increase for increasing Cu/Ca ratios (left to right in Figure ) regardless of P content. This is in agreement with the thermodynamic stability calculations (see Figure ) that predict the highest p-type dopability under Ca-poor conditions, suggesting CaCuP can tolerate significant Ca under-stoichiometry. The second trend is a conductivity drop when P/(Cu + Ca) > 1 (moving upwards in Figure ), i.e. under P-rich growth conditions. This is in disagreement with the thermodynamic stability calculations, which predict that significant P over-stoichiometry (combined with metal under-stoichiometry) affords the best p-type growth conditions. However, our experiments show that increasing P content leads to a decline in crystalline quality, which may be at least partially responsible for the drop in conductivity. The trends in average c-axis texturing versus P content (Figure ) also favour a higher conductivity in P-poor films because our measurement technique probes transport in the plane of the substrate. Specifically, a higher mobility is expected in the substrate plane for increasing c-axis texturing because the hole effective mass in CaCuP is around 4 times larger in the Γ → A direction (Figure , † corresponding to the c-axis in real space) compared to other high symmetry directions. This is illustrated in the hole density visualisation, Figure . A separate film (Ca:Cu:P = 1.03:1.09:1.00) was deposited in the shape of a Hall cross for further electrical measurements. At room temperature, the (Hall) hole concentration is 1.15 × 10 20 cm -3 and the (Hall) hole mobility is 36.4 cm 2 V -1 s -1 (Figure ). It is interesting to compare these properties to the case of state-of-the-art TCMs without extrinsic doping. Among p-type materials, CuI is one of the compounds with the highest figures of merit. Its highest reported hole concentration and mobility when deposited as a thin film are 1 × 10 20 cm -3 and 9 cm 2 V -1 s -1 respectively, and 1 × 10 18 cm -3 and 110 cm 2 V -1 s -1 when grown as a single crystal. Among the best n-type TCMs with a long research history (In 2 O 3 and ZnO), free electron concentrations in non-epitaxial, intrinsically doped films are generally below 4 × 10 20 cm -3 and electron mobilities are below 40 cm 2 V -1 s -1 . The electrical properties of p-type CaCuP films are therefore on par with the best n-type intrinsic TCMs . Fig. Hall measurements on a near-stoichiometric CaCuP film in the 10 K to 300 K temperature range. Hall hole concentration and mobility plotted in blue and red, respectively. The phonon-limited mobility fit in green is to a generic power law, µ p (T ) ≡ AT γ , while the fit in black is to the analytically derived expression for optical-phonon limited mobility,