  We present observations of an anisotropic resistance state at Landau level
filling factor $\nu=5/2$ in a two-dimensional hole system (2DHS), which occurs
for certain values of hole density $p$ and average out-of-plane electric field
$E_\perp$. The 2DHS is induced by electric field effect in an undoped
GaAs/AlGaAs quantum well, where front and back gates allow independent tuning
of $p$ and $E_\perp$, and hence the symmetry of the confining potential. For
$p\approx2\times10^{11}$~cm$^{-2}$ and $E_\perp \approx -2 \times10^{5}$~V/m,
the magnetoresistance along $\langle01\bar1\rangle$ greatly exceeds that along
$\langle011\rangle$, suggesting the formation of a quantum Hall nematic or
`stripe' phase. Reversing the sign of $E_\perp$ rotates the stripes by
$90^{\circ}$. We suggest this behavior may arise from the mixing of the hole
Landau levels and a combination of the Rashba and Dresselhaus spin-orbit
coupling effects.

Mesoscale and Nanoscale Physics