  A new algorithm for extracting de Haas-van Alphen frequencies and effective
masses from calculated band energies is presented. The algorithm creates an
interpolated k-space "super cell," which is broken into slices perpendicular to
the desired magnetic field direction. Fermi surface orbits are located within
each slice, and de Haas-van Alphen frequencies and effective masses are
calculated. Orbits are then matched across slices, and extremal orbits
determined. This technique has been successful in locating extremal orbits not
previously noticed in the complicated topology of existing UPt3 band-structure
data; these new orbits agree with experimental de Haas-van Alphen measurements
on this material, and solidify the case for a fully-itinerant model of UPt3.
