- The atomic structure of a new ternary phase UFe 2 Al 10 appearing in the U–Fe–Al system was determined using direct methods applied to X-ray powder diffraction data. High resolution electron microscopy combined with the methods of crystallographic image processing was used for the verification of the structural model. The UFe 2 Al 10 phase is orthorhombic and belongs to Cmcm space group, its unit cell contains 40 Al, eight Fe, and four U atoms. The lattice parameters obtained after Rietveld refinement are: a= 8.919 Å, b= 10.208 Å, and c= 9.018 Å. The reliability factors characterizing the Rietveld refinement procedure are: R p= 5.9%, R wp= 8.1%, and R b= 2.9%.