  Co$_2$MnGa is a ferromagnetic semimetal with Weyl nodal lines identified by
ARPES. We studied electrical transport in thin Co$_2$MnGa lamellae (10 $\times$
10 $\times$ 0.4-5 microns) cut from single-crystals using a focused ion beam.
These crystals exhibit an unexpected and highly unusual planar resistance
anisotropy ($\sim$10 times) with principal axes that rotate by 90 degrees
between the upper and lower faces. Using symmetry arguments and simulations, we
find that the observed resistance anisotropy resembles that of an isotropic
conductor with anisotropic surface states that are impeded from hybridization
with bulk states. The origin of these states awaits further experiments that
can correlate the surface bands with the observed 90$^\circ$-twist geometry.
