Gallium was deposited on a molybdenum tip by making contact between the tip and liquid gallium in vacuum. Pseudomorphic gallium could not be observed clearly. The product of the Mo&sngbnd;Ga reaction above 600 °C was found to be the ordered alloy, Mo3Ga, with the &bgr;‐W structure and no other structure was observed. The difference between the crystal structure and the observed image of the (001), (130), (120), and (110) planes of the alloy are explained by the unobservability of the gallium atom and by the variation of the stability of the molybdenum surface atoms. The observed differences in the stability of the surface atoms on these planes are interpreted in terms of anisotropic binding forces in the &bgr;‐W structure of the alloy.