Heat capacity of adsorbed sup 3 He at low Millikelvin temperatures.

The heat capacity of sup 3 Hee adsorbed on a silver powder substrate has been measured for temperatures between 0.4 and 7 mK and for coverages up to 5 atomic layers. The data show several features in common with those obtained for the sup 3 He-on-graphite system, including an anomaly in the exchange contribution to the heat capacity near 2 1/2 layers. In the graphite-substrate experiments the anomaly is associated with the freezing of the second sup 3 He layer. The second layer on the silver substrate, however, is found not to solidify.