  Motivated by recent proposal by Potter et al. [Phys. Rev. X 6, 031026 (2016)]
concerning possible thermoelectric signatures of Dirac composite fermions, we
perform a systematic experimental study of thermoelectric transport of an
ultrahigh-mobility GaAs/AlxGa1-xAs two dimensional electron system at filling
factor v = 1/2. We demonstrate that the thermopower Sxx and Nernst Sxy are
symmetric and anti-symmetric with respect to B = 0 T, respectively. The
measured properties of thermopower Sxx at v = 1/2 are consistent with previous
experimental results. The Nernst signals Sxy of v = 1/2, which have not been
reported previously, are non-zero and show a power law relation with
temperature in the phonon-drag dominant region. In the electron-diffusion
dominant region, the Nernst signals Sxy of v = 1/2 are found to be
significantly smaller than the linear temperature dependent values predicted by
Potter et al., and decreasing with temperature faster than linear dependence.
