*3.3.2. Sn0.97Cd0.03Se*

As an alloy with contrasting behavior, we show the transport properties of Sn0.97Cd0.03Se (**Figure 8b**, **d**, **f**). The cadmium-doped SnSe is the system with the highest Seebeck coefficients in this study (**Table 1**). Conversely, the electrical conductivity is very poor at RT, but there is an extraordinary increase with temperature, as illustrated in **Figure 8** on the right (middle panel). Both the large Seebeck coefficient and the low electrical conductivity indicate very low charge concentration. The steady decrease of the Seebeck coefficient (highest at 500 K with 570 μV/K) accompanied by the rapid increase of the electrical conductivity is another manifestation of the Pisarenko relationship [6]. The exponential temperature dependence of σ indicates a gap of E<sup>g</sup> = 0.6 eV. This is very similar to the intrinsic gap of SnSe. We can conclude from this study that Cd is unlikely to be a useful dopant for SnSe since its power factor is rather small, probably because of a lack of effective charge transfer (i.e. doping).
