We report the first observation of a sharp heat-capacity signature related to the superfluid transition in thin ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films adsorbed on porous Vycor and xerogel glasses. The transition temperatures of these films range from 0.14 to 1.1 K. This new feature is found in addition to the broad peak centered at a higher temperature reported in a number of earlier studies.

• Received 25 July 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.1954