Tetra Point Wetting at the Free Surface of Liquid Ga-Bi
  A continuous surface wetting transition, pinned to a solid/liquid/liquid/vapor tetra coexistence point, is studied by x-ray reflectivity in liquid Ga-Bi binary alloys. The short-range surface potential is determined from the measured temperature evolution of the wetting film. The thermal fluctuations are shown to be insufficient to induce a noticeable breakdown of mean-field behavior, expected in short-range-interacting systems due to their $d_u=3$ upper critical dimensionality. 
Patrick Huber (1), Oleg G. Shpyrko (1), Peter S. Pershan (1), Benjamin   M. Ocko (2), Elaine DiMasi (2), Moshe Deutsch (3) (...