in magnesium alloys cross slip can occur in two conditions : first when you increase temperature the amount of SFE increases and it will be possible to cross slip in both basal and prismatic planes and it is worth mentioning that by increasing temperature non-basal slip systems would be activated and cross slip becomes easier. The second fact is that if you add rare earth element to magnesium alloys, these elements would decrease the ratio c/a and this ratio will become smaller and close to 1.623 which is the ideal ratio for the tetragonality factor in HCP systems, hence non-basal slip systems will be activated and cross slip would be possible.