If there is a
temperature gradient across a
current and that current is inside and
perpendicular to a
magnetic field, a small but significant
electric field can be measured perpendicular to both the current and the magnetic field.
This is in addition to the larger
Hall voltage that can be measured due to
the Hall effect which occurs from the same set up when there is no temperature gradient.
This effect was discovered by Polish Physicist Walter Nernst for his PhD thesis in collaboration with Albert von Ettinghausen in 1887.