Synthesis, flux crystal growth, structure and properties of the new rare-earth compounds EuAl4−xSix (x ∼ 1), TmAlSi and LuAlSi

Reported are the crystal growth and properties of two new stoichiometric TmAlSi and LuAlSi compounds, crystallizing with the C-centered orthorhombic YAlGe-type, and of the non-stoichiometric EuAl4−xSix (x ∼ 1), a ternary derivative of the body-centered tetragonal BaAl4-type. All three compounds were synthesized from reactions of the corresponding metals, and using an excess of elemental aluminum as a flux. Their crystal structures were determined by single-crystal X-ray crystallography: space group Cmcm (No. 63) with cell parameters a = 3.9638(7) Å, b = 10.116(2) Å and c = 5.6314(10) Å for TmAlSi, and a = 3.964(2) Å, b = 10.034(4) Å and c = 5.598(3) Å for LuAlSi, respectively, and space group I4/mmm (No. 139) with a = 4.3826(11) Å and c = 10.785(6) Å for EuAl2.96(2)Si1.04(2), respectively. Magnetization measurements carried out as a function of the temperature suggest the Eu- and the Tm-compounds to order magnetically below ∼17 K and ∼6 K, respectively.