A new ternary compound YbZn2As2 with mixed valency of Yb

A new compound with chemical formula YbZn₂As₂ and ‘anti’-La₂O₃-type crystal structure (space group P3m1) has been synthesized for the first time. The trigonal lattice constants of the compound are a=0.4157 and c=0.6954 nm. In the temperature range 77–500 K, the magnetic susceptibility of YbZn₂As₂ follows the Curie–Weiss law, indicating antiferromagnetic interactions of the Yb ions and yielding a Curie temperature θ=−52.8 K and an effective magnetic moment μ_eff=2.35 μ_B (the Bohr magneton) per Yb ion. This means that a part of the Yb ions has valency 3+, instead of 2+ for all the Yb ions, as would be expected from their formal oxidation number, i.e. YbZn₂As₂ is a compound with mixed valency of Yb. YbZn₂As₂ exhibits p-type conductivity with a room temperature electrical resistivity of 0.15 Ω cm which decreases when lowering temperature and reaches a practically constant value of 0.08 Ω cm below 20 K.