Intermetallic phases with Ho₄Ir₁₃Ge₉-type structure

Abstract We report on the synthesis an structural characterization of 16 new tetrelides RE -(Rh,Ir)-(Si,Ge), the phosphides Sm 4 Rh 13 P 9 , Sm 4 Ir 13 P 9 , Gd 4 Ir 13 P 9 and Yb 4 Ir 13 P 9 and the arsenide Eu 4 Ir 13 As 9 , which crystallize with the orthorhombic Ho 4 Ir 13 Ge 9 type. The structure of Gd 4 Ir 13 Ge 9 was refined from single-crystal X-ray diffractometer data: space group Pmmn , a = 397.76(2), b = 1,120.97(6), c = 1,935.52(10) pm, w R 2 = 0.0683, 2,537 F 2 values and 90 refined variables. The iridium and germanium atoms in Gd 4 Ir 13 Ge 9 build up a three-dimensional [Ir 13 Ge 9 ] polyanionic network which is stabilized by Ir–Ge (240–260 pm) and Ir–Ir (274–294 pm) bonding interactions. The three crystallographically independent gadolinium sites fill large channels within the [Ir 13 Ge 9 ] polyanionic network. They have hexagonal prismatic coordination with additional atoms capping the rectangular faces. The structural chemistry of the Ho 4 Ir 13 Ge 9 type is compared to the hexagonal phases RE 4 Co 13 (Si,P) 9 ( RE = Sm, Gd–Er), U 4 Fe 13 P 9 and the auride Sr 4 In 13 Au 9 . Magnetic susceptibility data of Tb 4 Ir 13 Ge 9 show Curie-Weiss behavior with an experimental magnetic moment of 10.4(1) µ B Tb atom −1 . Tb 4 Ir 13 Ge 9 is ordered antiferromagnetically at T N = 4.7(1) K and undergoes two successive metamagnetic steps.