  We report on the thermopower of an Aharonov-Bohm interferometer (AB) with a
quantum dot in the Kondo limit. The thermopower is anomalously enhanced due to
the Kondo effect as in heavy fermion systems. In contrast to the bulk systems,
the sign of the thermopower can be changed by adjusting the energy level scheme
or the particle-hole asymmetry of a dot with the gate voltage. Further the
magnitude and even the sign of the thermopower in the AB ring can be changed at
will with varying either magnetic fields or the gate voltages.
