  Consider a layer made of a m3m insulator crystal, with faces cut parallel to
a symmetry plane. Then bond it onto a semi-infinite mm2 piezoelectric
substrate. For a X- or Y -cut of the substrate, a Love wave can propagate in
the resulting structure and the corresponding dispersion equation is derived
analytically. It turns out that a fully explicit treatment can also be
conducted in the case of a Y -cut rotated about Z. In the case of a germanium
layer over a potassium niobate substrate, the wave exists at any wavelength for
X- and Y -cuts but this ceases to be the case for rotated cuts, with the
appearance of forbidden ranges. By playing on the cut angle, the Love wave can
be made to travel faster than, or slower than, or at the same speed as, the
shear bulk wave of the layer. A by-product of the analysis is the derivation of
the explicit secular equation for the Bleustein-Gulyaev wave in the substrate
alone, which corresponds to an asymptotic behavior of the Love wave.
