The electrical resistances of oriented single crystals of TmB12 and Ho
B12 in the temperature range 1.6-10 K are reported. From the temperatu
re derivatives of the resistances the corresponding Neel temperatures
TN have been determined. The temperature dependence of the d.c. magnet
ic susceptibility of HoB12 down to 5 K has also been measured and conf
irms the antiferromagnetic nature of the phase transition.