Using a low-temperature MBE growth procedure, Ga1-xMnxAs is obtained with Mn concentrations up to x approximate to 9%. At a temperature around 50 K, a paramagnetic to ferromagnetic phase transition occurs as a result of the interaction between Mn-h complexes. A model based on a mean-field approach explains the observed temperature dependence of the magnetisation. The magnetic behaviour is linked to the magnetotransport features. (C) 1998 Elsevier Science B.V. All rights reserved.