[en] The U-Al-Si system was investigated in the composition range from U to U-80 at.% Al to U-75 at.% Si. More than 260 binary and ternary alloys were arc melted and studied by metallographic and x-ray powder diffraction techniques, in the as-cast condition and after thermal treatment at temperatures ranging from 700 to 1040⁰C. One or possibly two ternary compounds of undetermined crystal structure exist at or near U₂AlSi₂. The binary silicides U₃Si, U₃Si₂, and USi can dissolve only small amounts of Al in solid solution, but the higher silicides U₃Si₅, USi_2-x, and USi₃ dissolve increasingly larger amounts of Al. Of the three binary aluminides, UAl₂ can dissolve more than 12 at.% Si in solid solution. UAl₃ forms a continuous solid solution with USi₃, and UAl₄ is not present in alloys containing more than 3 at.% Si