  We report on a study of the Nernst effect in graphite extended up to 45 T.
The Nernst response sharply peaks each time a Landau tube is squeezed inside
the thermally fuzzy Fermi surface and presents a temperature-independent fixed
point whenever the tube flattens to a single ring. Beyond the quantum limit,
the onset of the field-induced phase transition leads to a drastic drop in the
Nernst response signaling the sudden vanishing of Landau tubes. The magnitude
of this drop suggests the destruction of multiple Landau tubes possibly as a
result of simultaneous nesting of the electron and hole pockets.
