With the aid of the Kadanoff-Baym transport equations, the high-field Hall coefficient is calculated for holes in narrow bands according to Hubbard's model. It is found that the inverse Hall coefficient is proportional to the fraction of momentum space occupied by the holes, which in Hubbard's model does not equal the number of holes per atom. Therefore, the holes would not be compensated by the conduction electrons, and it is concluded that Hubbard's model in its present form is inapplicable to even-valence transition metals such as palladium and platinum.

• Received 12 July 1965

DOI:https://doi.org/10.1103/PhysRev.148.707