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.