Critical behavior of the Hall coefficient of Si:B

Measurements between 0.05 and 1 K in magnetic fields small enough to ensure linear response (B1 T) indicate that the Hall coefficient of Si:B diverges at the metal-insulator transition. This is similar to Ge:Sb and differs from the finite behavior claimed for Si:As and Si:F. Our result may be due to strong spin-orbit effects; it is inconsistent with a recent suggestion that the Hall coefficient is finite in systems with critical conductivity exponent {μ}{}1/2.