  The zero-temperature magnetoconductivity of just-metallic Si:P scales with
magnetic field, H, and dopant concentration, n, lying on a single universal
curve. We note that Si:P, Si:B, and Si:As all have unusually large magnetic
field crossover exponents near 2, and suggest that this anomalously weak
response to a magnetic field is a common feature of uncompensated doped
semiconductors.
