Multiple ordered phases in the filled skutterudite compound PrOs${}_4$As${}_{12}$

Magnetization, specific heat, and electrical resistivity measurements were made on single crystals of the filled skutterudite compound PrOs${}_4$As${}_{12}$. Specific heat measurements indicate an electronic specific heat coefficient $\gamma$ $\sim 50-200$ mJ/mol K${}^2$ at temperatures 10 K $\le T\le 18$ K, and $\sim 1$ J/mol K${}^2$ for $T\le 1.6$ K. Magnetization, specific heat, and electrical resistivity measurements reveal the presence of two, or possibly three, ordered phases at temperatures below $\sim 2.3$ K and in fields below $\sim 3$ T. The low temperature phase displays antiferromagnetic characteristics, while the nature of the ordering in the other phase(s) has yet to be determined.