Strongly anisotropic electronic transport at landau level filling factor ν=9/2 and ν=5/2 under a tilted magnetic field

We have investigated the influence of an increasing in-plane magnetic field on the states of half filling of Landau levels (ν=11/2, 9/2, 7/2, and 5/2) of a two-dimensional electron system. In the electrically anisotropic phase at ν=9/2 and 11/2 an in-plane magnetic field of ∼1-2T overcomes its initial pinning to the crystal lattice and reorients this phase. In the initially isotropic phases at ν=5/2 and 7/2 an in-plane magnetic field induces a strong electrical anisotropy. In all cases, for high in-plane fields the high-resistance axis is parallel to the direction of the in-plane field.