  The low-temperature resistivity of a SiGe 2-dimensional hole gas has been
studied using the gate controlled carrier density as a parameter. A
metal-insulator transition is seen both in the temperature and in the electric
field behaviour. Values of 1 for the dynamical exponent and 2.85 for the
correlation length exponent are obtained from scaling plots. No quenching of
the metallic phase in a parallel magnetic field is observed. Since in our
system there is an easy axis for magnetization, this result supports the
hypothesis that the transition is related to spin interactions.
