  Nernst effect has been measured for an underdoped and an optimally doped
$La_{2-x}Sr_xCuO_4$ single crystal with the magnetic field applied along
different directions. For both samples, when $H \|$ c, a significant Nernst
voltage appears above $T_c$ and keeps measurable up to a high temperature (100
K) as reported by Xu et al.[ Nature 406, 486(2000) ]. However, when $H \|$ a-b
plane the Nernst signal drops below the noise level quickly above $T_c$ for the
underdoped sample. Moreover, the in-plane Nernst data with field at different
angles shows a nice scaling behavior with the c-axis component of the field.
All these give strong indication for strictly in-plane vortex-like excitations
in pseudo-gap region.
