Flux synthesis, structure and physical properties of new pseudo-binary REAl3-xGex compounds

New compounds in the system RE-Al-Ge (RE=Tb, Gd, Ho) were prepared in molte n aluminum. Large, (up to 5 mm) single crystals of new pseudo-binary phases GdAl3-xGex, (x=0.1), TbAl3-xGex, (x=0.3), and HoAl3-xGex, (x=0.2) were rec overed in high yield. The crystal structures were refined by single crystal X-ray diffraction techniques, and found to vary as a function of rare-eart h element. Thus, GdAl3-xGex crystallizes in the Ni3Sn structure type (P6(3) /mmc) of GdAl3. For the TbAl3-xGex the BaPb3 structure type (R-3m) is adopt ed, as it is for TbAl3. In the case of HoAl3-xGex, the structure type of Ho Al3 is not stabilized, and the compound crystallizes in the BaPb3 structure (R-3m). Crystal data: GdAl3-xGex a=6.3115(4) Angstrom, c=4.6052(4) Angstro m, V=158.87(2) Angstrom (3), P6(3)/mmc (No. 194, 2=2); TbAl3-xGex a=6.1956( 9) Angstrom, c=21.025(4) Angstrom, V=698.9(2) Angstrom (3), R-3m (No. 166, Z=9); HoAl3-xGex a=6.1579(10) Angstrom, c=21.062(5) Angstrom, V=691.7(2) An gstrom3, R-3m (No. 166, Z=9). Charge transport properties indicate that the se materials are good metallic conductors. At low temperatures they order a ntiferromagnetically, whereas above similar to 50 K they are Curie-Weiss pa ramagnets. The temperature of maximum magnetic susceptibility (T-max) is 5. 93 K, 18.8 K, and 24.0 K for HoAl2.8Ge0.2, TbAl2.7Ge0.3, and GdAl2.9Ge0.1 r espectively. (C) 2001 Elsevier Science B.V. All rights reserved.