Does the Hall coefficient exhibit critical behavior approaching the metal-insulator transition?

Hall-effect measurements on uncompensated barely metallic Si:As samples have been made at temperatures between 4.2 and 0.5 K with the objective of obtaining the Hall coefficient as the magnetic field H and T approach zero. The Si:As results and a reanalysis of earlier Si:P data do not yield critical behavior of ${\mathrm{R}}_{\mathrm{H}}^{\mathrm{-}1}$ contrary to recently reported results for Ge:Sb and other systems. The results agree with localization-theory predictions.