Geometric contribution to the measurement of thermoelectric power and Nernst coefficient in a strong magnetic field

For the measurement of thermoelectric power and Nernst coefficient, we used two kinds of shapes for a sample. One is the "bridge shape" and the other is, we call, "fat-bridge shape". The latter has 5 times wider main body than the former. We used pure n-InSb in this experiment, whose carrier concentration measured at 77 K was 6.6/spl times/10/sup -14/ cm/sup -3/. The length of sample is 17 mm and the temperature difference induced between the edges in that direction was about 10/spl deg/C or 100/spl deg/C near the room temperature range of 0 to 100/spl deg/C. Magnetic induction added in the perpendicular direction to the temperature gradient was in the range of 0 up to 4 Tesla. In the case of "fat bridge shape", we detected about 10% smaller Nernst coefficient and 1 to 10% smaller thermoelectric power comparing to the "bridge shape". We suppose this phenomena is due to the geometric contribution on the different shape of samples.