  A prototype experiment to measure the neutron electric dipole moment (nEDM)
by spin-rotation in a non-centrosymmetric crystal in Laue geometry was carried
out in order to investigate the statistical sensitivity and systematic effects
of the method. The statistical sensitivity to the nEDM was about $6\cdot
10^{-24}$ e$\cdot $cm per day and can be improved by one order of magnitude for
the full scale setup. Systematics was limited by the homogeneity of the
magnetic field in the crystal region and by a new kind of spin rotation effect.
We attribute this effect to a difference of the two Bloch waves amplitudes in
the crystal, which is caused by the presence of a small crystal deformation due
to a temperature gradient. In a revised scheme of the experiment, this effect
could be exploited for a purposeful manipulation of the Bloch waves.
