Crystal structure and physical properties of the novel ternary intermetallics URuSi3−x and U3Ru2Si7

Two novel ternary intermediate phases, namely URuSi3−x (x=0.11) and U3Ru2Si7 were found in the Si-rich part of the U–Ru–Si phase diagram. Single crystal X-ray diffraction measurements, carried out at room temperature, indicated that URuSi3−x crystallizes in its own tetragonal type structure (space group P4/nmm, no. 129; unit cell parameters: a=12.108(1) Å and c=9.810(1) Å), being a derivative of the BaNiSn3-type structure. U3Ru2Si7 adopts in turn a disordered orthorhombic La3Co2Sn7-type structure (space group Cmmm, no. 65; unit cell parameters: a=4.063(1) Å, b=24.972(2) Å and c=4.072(1) Å). As revealed by magnetization, electrical resistivity and specific heat measurements, both compounds order magnetically at low temperatures. Namely URuSi3−x is a ferromagnet with TC=45 K, and U3Ru2Si7 shows ferrimagnetic behavior below TC=29 K.