The low temperature thermoelectric power of a doped superlattice as a function of the Fermi energy (band filling) locates the positions of the edges of the minibands. The thermoelectric power is anisotropic according to whether the temperature gradient is along or perpendicular to the superlattice axis: for momentum relaxation rates proportional to the density of final states and for the Fermi energy in the gap between minibands, it vanishes in the former case, but not in the latter. For the Fermi level near the tops of the minibands, a sign reversal is predicted indicative of hole-like behaviour.