  We explain for the first time thermopower data for p-type GaAs/AlGaAs layers.
The data span a temperature range between 0.2 to 1.2K. We calculate both the
diffusion $S^{d}$ and the phonon-drag $S^{g}$ contributions to the thermopower.
We find that $S^{d}$ is significant for temperatures up to 0.3K while at higher
temperatures $S^{g}$ dominates. The calculated and measured $S^{g}$ agree very
well with no adjustable parameters.
