Turbine accessory drive gearbox assembly in an airplane engine such as a jet engine

The gearbox has a casing (10) mounted with a coiled stator (18) of an electric machine e.g. alternator (16), whose rotor (14) is guided in a bearing (24) e.g. roller bearing, carried by a support part (40). The support part is carried by an annular part (42) of the machine and is made of reduced thermal dilation coefficient material e.g. titanium. The annular part is applied on the casing and is made good heat conducting material e.g. aluminum, having thermal conductivity higher than the thermal conductivity of the support part for forming a thermal bridge between the stator and the casing.