 In principle all fermion energy level populations are bound by a Fermi surface although the term is not generally used outside of condensed-matter physics.Electronic Fermi surfaces have been measured through observation of the oscillation of transport properties in magnetic fields formula_29, for example the de Haas–van Alphen effect (dHvA) and the Shubnikov–de Haas effect (SdH).The former is an oscillation in magnetic susceptibility and the latter in resistivity.