Antiferromagnetic Arsenides U ₈ Co ₄₂ As ₂₅ and UCo ₃ As ₂

High Resolution Image Download MS PowerPoint Slide Arsenides continue to captivate the fields of inorganic chemistry and condensed matter physics. In this work we present the discovery of two new members of this family─U 8 Co 42 As 25 and UCo 3 As 2 ─which were synthesized in single crystalline form. U 8 Co 42 As 25 is the first representative of the Y 8 Co 41 As 25 structure type (space group P 6 3 / m, Pearson symbol hP 75, a = 17.7460(5) Å, c = 3.8120(1) Å), while UCo 3 As 2 adopts HoCo 3 P 2 type of structure (space group Pmmn, Pearson symbol oP 36, a = 3.8611(2) Å, b = 10.8414(6) Å, c = 12.7297(6) Å). Both materials order antiferromagnetically─U 8 Co 42 As 25 at T N = 26 K and UCo 3 As 2 at T N = 67 K.