We present a linear-response theory for the thermopower of a single-electron transistor consisting of a superconducting island weakly coupled to two normal-conducting leads. The thermopower shows oscillations with the same periodicity as the conductance and is rather sensitive to the size of the superconducting gap $\Delta$. In particular, the previously studied sawtooth-like shape of the thermopower for a normal-conducting single-electron device is qualitatively changed even for small gap energies.

• Received 10 March 2005

DOI:https://doi.org/10.1103/PhysRevB.71.220503