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(Color online) Experimentally measured thermopower (asterisks) at different values of doping for at . The theoretical Heikes curve is provided alongside for comparison. It can be seen that the experimental values are close to the theoretical ones, showing that the Heikes limit is a good approximation at . The values are systematically lower since the Heikes limit is approached from below in temperature.
(Color online) at for different values of doping for (with ) assuming different values of the the phonon thermal conductivity (assumed to be doping independent). adds to from Eq. (10).
(Color online) Power factor as a function of doping for as predicted by theory. There are maxima at , , , and . The last two values can be realized in the material, in principle, at doping values and . The positions of the peak are independent of the material parameters in this calculation and a peak at has indeed been seen in experiments on .
(Color online) at a particular temperature for an arbitrary system. All material dependent parameters are assumed to be the same for the different values of . The slight peak shift is due to the weak logarithmic dependence of on .
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