Well-ordered (Formula presented) alloy films of up to two ML thickness were grown on top of a W(110) substrate and characterized by using scanning tunneling microscopy/spectroscopy (STM/STS) and low-energy electron diffraction (LEED). The crystallographic structure of the ultrathin films was found to be different from the well-known bulk structure (C15 Laves phase). This is supposed to result from the influence of the substrate on the growth behavior. Based on atomically resolved STM images and LEED studies, a structure model for the ultrathin (Formula presented) films on W(110) is proposed.