Single-crystal Sm(00•1) surfaces were grown epitaxially on Mo(110). At low temperatures low-energy electron diffraction showed a 5 x 5 surface reconstruction. This new type of valence-transition-induced reconstruction corresponds to a 25% expansion of the interatomic distances in the topmost hexagonal surface layer. At room temperature the 5 x 5 low-energy electron diffraction pattern disappeared due to a disordering of the surface. This suggests a very low melting temperature for the surface which could have implications for the understanding of the anomalous melting temperature of Sm metal.

Valence-Transition-Induced 5 x 5 Surface Reconstruction of Sm(0001). A.Stenborg, J.N.Andersen, O.Björneholm, A.Nilsson, N.Mårtensson: Physical Review Letters, 1989, 63, 187-90