Syntheses, structures, and physical properties of LnAsTe (Ln = La, Pr, Sm,Gd, Dy, Er)

Six rare-earth arsenic tellurides have been synthesized by the reactions of the rare-earth elements (Ln) with As and Te at 1123 K. LaAsTe (a = 7.8354( 11) Angstrom, b = 4.1721(6) Angstrom, c = 10.2985(14) Angstrom, T = 153 K), PrAsTe (a = 7.728(2) Angstrom, b = 4.1200(11) Angstrom, c = 10.137(3) Angs trom, T = 153 K), SmAsTe (a = 7.6180(16) Angstrom, b = 4.0821(9) Angstrom, c = 9.991(2) Angstrom, T = 153 K), GdAsTe (a = 7.5611(15) Angstrom, b = 4.0 510(8) Angstrom, c = 9.920(2) Angstrom, T = 153 K), DyAsTe (a = 7.4951(13) Angstrom, b = 4.0246(7) Angstrom, c = 9.8288(17) Angstrom, T = 153 K), and ErAsTe (a = 7.4478(1) Angstrom, b = 4.0078(1) Angstrom, c = 9.7552(2) Angst rom, T = 153 K) crystallize with four formula units in the orthorhombic spa ce group D-2h(16)-Pnma. These compounds are isostructural and belong to the B-ZrSb2 structure type. Tn each compound, the Ln atoms are coordinated by a tricapped trigonal prism of four As atoms and five Te atoms. The entire t hree-dimensional structure is built up by the motif of the LnAs(4)Te(5) tri capped trigonal prisms. Infinite nonalternating zigzag As chains are found along the b axis, with As-As distances in these compounds ranging from 2.59 15(5) to 2.6350(9) Angstrom. Conductivity measurements in the direction of these As chains indicate that PrAsTe is metallic whereas SmAsTe and DyAsTe are weakly metallic. Antiferromagnetic transitions occur in SmAsTe and DyAs Te at 3 and 9 K, respectively. DyAsTe above 9 K follows the Curie-Weiss law .