  We present the first measurement on Nernst effect in the normal state of
odd-parity, spin-triplet superconductor Sr$_{2}$RuO$_{4}$. Below 100 K, the
Nernst signal was found to be negative, large, and, as a function of magnetic
field, nonlinear. Its magnitude increases with the decreasing temperature until
reaching a maximum around $T^*$ $\approx$ 20 - 25 K, below which it starts to
decrease linearly as a function of temperature. The large value of the Nernst
signal appears to be related to the multiband nature of the normal state and
the nonlinearity to band-dependent magnetic fluctuation in Sr$_{2}$RuO$_{4}$.
We argue that the sharp decrease in Nernst signal below $T^*$ is due to the
suppression of quasiparticle scattering and the emergence of band-dependent
coherence in the normal state. The observation of a sharp kink in the
temperature dependent thermopower around $T^*$ and a sharp drop of Hall angle
at low temperatures provide additional support to this picture.
