With YBa2Cu3O7 samples inserted into the microwave (f(p) similar to 9
GHz) microstrip resonator cavity instead of the identical Nb sample we
have found a significant broadening of the resonant curve along with
an enhanced resonator transmittivity. These changes were accompanied b
y the appearance of a new intense and broad resonant transmission band
. The results obtained are interpreted as a manifestation of the diele
ctric resonance in HTSC samples induced by the microwave electromagnet
ic field.