A new roughening transition has been observed on hcp ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ crystals at $T=0.365\mathrm{}\pm 0.03$ K, where a third kind of facet appears at 60±3° from the basal planes. The authors relate this experimental observation to the arguments presented recently against the existence of quantum roughening. Some preliminary results concerning the growth of facets are also briefly mentioned.

• Received 31 May 1983

DOI:https://doi.org/10.1103/PhysRevLett.51.1366