The manner is discussed in which the wave vector surface anisotropy of
paratellurite reflects on the diffraction divergence of quasi-transve
rse wave beams near the preferred [110] direction. Analytical expressi
ons are derived for the principal curvature tensor values that charact
erize the diffraction beam spread in the (001) and (1(1) over bar0$) c
oordinate planes. An experimental study is undertaken into the changes
that the beam suffers in direction and shape as it is scanned near th
e [110] direction.