A noticeable magnetic field dependence of the vortex lattice distortio
ns in hexagonal unconventional superconductors is obtained below the s
econd order phase transition line H(T) (H*(T) < H-c2(T)) for ($) over
right arrow H perpendicular to the hexagonal axis ($) over right arro
w c. The range of the Ginzburg-Landau coefficients is shown to exist w
here our theoretical results are in a qualitative agreement with the n
eutron diffraction measurements in UPt3.