EPR spectra on metal-insulator transitions in compensated Ge : As

Principal changes of the electron paramagnetic resonance (EPR) in compensat ed Ge:As were found at the metal-insulator transition. EPR spectrum of meta llic samples includes the Dyson line with the width increasing by the compe nsation. In the insulator samples this line is split into two when the temp erature is lower than 4.1 K. The first one remains immovable and the second one moves to stronger magnetic fields when the temperature decreases. Whil e the anomalous moving line has only the positive part of the derivative, t he immovable line remains symmetrical. Other changes (in the temperature de pendence of the line form and of the spin relaxation time) were indicated, too. The nature of these changes is discussed.