"Hall Coefficient" is defined as the ratio of the induced electric field to the product of the current density and the applied magnetic field.
Applicable units are those of quantitykind:HallCoefficient
http://en.wikipedia.org/wiki/Hall_effect
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD060
"Hall Coefficient" is defined as the ratio of the induced electric field to the product of the current density and the applied magnetic field.
In an isotropic conductor, the relation between electric field strength, $E$, and electric current density, $J$ is $E = \rho J + R_H(B X J)$, where $\rho$ is resistivity, and $B$ is magnetic flux density.
http://www.iso.org/iso/catalogue_detail?csnumber=31897