Single needle-shaped crystals of U3ScSb5 and U3TiSb5 were grown in a tin flux. The structure of the new compound U3ScSb5 was determined from single-crystal X-ray diffraction data (Pearson symbol hP18, hexagonal, space group P63/mcm, Z = 2, a = 9.2145(2) A, c = 6.1938(2) A). The angular dependence of the magnetization has been studied. Ferromagnetic ordering develops within the ab plane at TC = 130 K for U3ScSb5 and 160 K for U3TiSb5, but there are essentially no magnetic interactions parallel to the c axis, confirming the high anisotropy expected from the crystal structure. In both cases, the easy axis for magnetization is the [120] direction. A sharp decrease below the ordering temperature is observed in the electrical resistivity parallel to the c axis; in contrast, the temperature dependence is much weaker within the ab plane. For U3TiSb5, a second transition occurs at 25 K, possibly arising from a spin reorientation process. The thermoelectric power measured along the c axis for both compounds is posi...