Magnetic and electrical properties of the ternary compound U2Ir3Si5 with one-dimensional uranium zigzag chains

The physical properties of the single-crystalline ${\mathrm{U}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$, a new ternary uranium compound with ${\mathrm{U}}_{2}{\mathrm{Co}}_{3}{\mathrm{Si}}_{5}$-type orthorhombic structure, are investigated by means of magnetic susceptibility $\ensuremath{\chi}(T)$, specific heat $C(T)$, electrical resistivity $\ensuremath{\rho}(T)$, and high-field magnetization $M(H,T)$ measurements. ${\mathrm{U}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ undergoes an antiferromagnetic transition at ${T}_{N}=36$ K followed by a first-order phase transition at ${T}_{0}=25.5$ K. The sharp peak in $C(T)$ at ${T}_{0}$ and the obvious hysteresis behavior in $\ensuremath{\chi}(T),\ensuremath{\rho}(T)$, and $M(H,T)$ around ${T}_{0}$ provide strong evidence for the first-order phase transition. The $\ensuremath{\rho}(T)$ measurements along the $a$ and $b$ axes reveal the negative temperature coefficients of resistance over a wide temperature range, which can be understood based on the semiconductorlike narrow band gap model or the Kondo effect. The $M(H)$ curve measured at 4.2 K along the $b$ axis shows three-step metamagnetic transitions within a narrow field region around 200 kOe and a large hysteresis near the first transition field, while the ${M}_{H\ensuremath{\parallel}a}(H)$ and ${M}_{H\ensuremath{\parallel}c}(H)$ curves show no transitions up to 560 kOe suggesting the strong magnetic anisotropy. A possible mechanism of the first-order phase transition at ${T}_{0}$ is the occurrence of a magnetic quadrupolar order, resulting from the quasi-one-dimensional uranium zigzag chain.