Nernst effect of the new iron-based superconductor LaO${}_{1-x}$F${}_x$FeAs

We report the first Nernst effect measurement on the new iron-based superconductor LaO${}_{1-x}$F${}_x$FeAs $(x=0.1)$. In the normal state, the Nernst signal is negative and very small. Below $T_c$ a large positive peak caused by vortex motion is observed. The flux flowing regime is quite large compared to conventional type-II superconductors. However, a clear deviation of the Nernst signal from normal state background and an anomalous depression of off-diagonal thermoelectric current in the normal state between $T_c$ and 50 K are observed. We propose that this anomaly in the normal state Nernst effect could correlate with the SDW fluctuations.