The first experimental study of the new effects predicted early was conducted, using the recently created set-up designed for searching a neutron EDM by the crystal-diffraction technique. The effect of a considerable delay of the diffracting neutron in the crystal for Bragg angles close to 90° and the effect of a depolarization of diffracting neutrons in the crystal without a centre of symmetry were first observed. The existence of the dynamical diffraction in a thick (14 × 14 × 3.5 cm3) noncentrosymmetric α-quartz crystal for Bragg angles up to 87° was demonstrated. It is experimentally shown that the value Eτ, where E is an electric field and τ is the interaction time, determined the sensitivity of the method to neutron EDM in our case can be ∼ 0.2 × 106 V s/cm, what is comparable with the Ultracold neutrons (UCN) method. © 2001 Elsevier Science B.V.