Isotopic mixtures of 70 Ge and 74 Ge (Isotopically Engineered: IE-Ge) were by a neutron-transmutation doping (NTD) process provided with a high compensation of K = N As /N Ga ffi 0.4, 0.6, 0.9. Variable range hopping (vrh) resistivity at T = 0.1-4.2 K shows r(T) = r 0 exp(T 0 /T) 1/2 . At K = 0.4-0.6 a small change of the critical concentration of the metal-insulator transition, N c and at K = 0.9 a very strong increase of up to N c = (1.2 AE 0.2) Â 10 19 cm --3 was found. We calculated the value of the localization length a from measurements of the temperature-and low-field dependencies of the positive magnetoresistance, and by a combination of a with T 0 = 2.8 e 2 /k B a4pe 0 j the dielectric constant j is estimated. In accordance with the predictions of a disorder-induced scaling theory, the critical indices n ffi 1, z ffi 2, and p ffi 3 were obtained for a, j and T 0 , respectively. At medium compensation, K 0.6, the value of T 0 is much smaller than T ES predicted by Efros and Shklovskii for one-electron-transitions, which is interpreted as being due to many-particle excitations which reduce the width of the Coulomb gap. Only at K = 0.9 and at very low impurity concentration far from the range of validity of the scaling relation many-particle excitations can be neglected, resulting in a strong increase of T 0 ! T ES ffi 366 K.