  The experimental research of the longitudinal ultrasound absorption in an
intermediate state of the high pure Ga single crystal at the frequencies of 30
- 130 MHz at the temperatures of 0.4 - 0.5 K, using the impulse method, is
completed. The new effects in the absorption of ultrasound in an intermediate
state of the high pure type I superconductor are discovered. The giant
oscillations in the dependence of the ultrasound absorption on the magnetic
field at the magnitudes below the critical magnetic field, H < Hc, in an
intermediate state of the high pure Ga single crystal are experimentally
observed The maximum of the monotonic part of the ultrasound absorption on the
magnetic field is also obtained. The additional experimental results in the
dependence of the ultrasound absorption on the frequency of longitudinal
ultrasonic wave f and on the orientation of external magnetic field are
reported. In the case of the high frequencies ultrasonic signal, the different
behaviour of the monotonous part of the dependence of the ultrasound absorption
on the magnetic field in an intermediate state, comparing to the theoretical
prediction [10], is found. The anomalous distinction in the dependence of the
ultrasound absorption on the orientation of magnetic field in an intermediate
state of Ga in comparison with the dependence of the ultrasound absorption in a
normal state of Ga at the same temperature and at the magnitude of magnetic
field equal to the critical magnetic field, H = Hc, is observed. The possible
theoretical mechanisms to explain the nature of big oscillations in the
dependence in an intermediate state of the high pure type I superconductor are
proposed.
