  The nonlinear absorption of radio waves (200 - 800 MHz) in a noncollinear
cubic antiferromagnet Mn3Al2Ge3O12 in an external magnetic field H || [001] has
been studied in the temperature range of 1.2 - 4.2 K. We attribute the observed
dissipation of the electromagnetic energy to the parametric excitation of
inhomogeneous surface waves at the boundaries of antiferromagnetic domains.
