  We have developed a theory of the negative magnetoresistance due to the weak
localization in uniaxial wurtzite-type crystals, in which the spin splitting of
the conduction band is linear in the wave vector, unlike the cubic ${\rm A_3
B_5}$ crystals. Unlike earlier theories, we take into account the correlation
between the electron motion in spin and co-ordinate spaces. It is shown that as
a result of this correlation the magnetoresistance depends on the orientation
of the magnetic field with respect to the main axis of the crystal even if the
effective mass is isotropic. The new theory allows to accurately determine the
value of the spin splitting constant in uniaxial crystals.
