High-Temperature Electrical and Magnetic Properties of Undoped Iron Pnicties

We have investigated the electrical and magnetic properties of several parent compounds of Fe-based superconductors in a wide temperature range. In addition to the well-known transitions (one structural transition at T$_{s}$ and one spin-density-wave (SDW) transition at T$_{M})$, all investigated parent compounds (BaFe$_{2}$As$_{2}$,$_{ }$SrFe$_{2}$As$_{2}$, LaFeAsO, FeTe) show unusual features in both magnetic susceptibility and electrical resistivity at high temperatures (T). Above T$_{s}$, their magnetic susceptibility increases more or less linearly with increasing temperature up to at least 700 K. On the other hand, the electrical resistivity exhibits non-monotonic temperature dependence, revealing non-metallic character at high temperatures. The implication of these results will be discussed.