The solidification of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in Vycor glass and in sintered Ag powder has been studied between 0.8 and 2.5 K. At 0.8 K, elevation of the melting pressure by 12 bars is seen in Vycor and by 0.3 bar in the Ag sinter. In each material a range of melting pressures, corresponding to different pore sizes, is observed. The location of the $\lambda$ transition in the liquid in Vycor is determined up to solidification pressure.

• Received 19 March 1984

DOI:https://doi.org/10.1103/PhysRevLett.52.2249