Co-doped ZnO films with Co content above 7% have been grown by pulsed laser deposition on a-sapphire substrates. Temperature and magnetic field dependent magnetotransport measurements have been performed on samples with electron concentration n around the critical electron concentration nc~4.9×1019 cm-3, where the metal-insulator transition (MIT) occurs. At 5 K we observed positive magnetoresistance (MR) in the insulating range (nnc).
