Angle-resolved de Haas-van Alphen measurements made on ThBe13 in pulsed mag
netic fields are compared with Fermi surface predictions calculated by mean
s of the linear augmented-plane-wave method with spin-orbit interactions. W
hile all of the experimentally determined qustsiparticle effective masses a
re light and of order the free electron mass, they are still roughly double
those obtained from the calculated band structure, thereby being suggestiv
e of the existence of notable electron-phonon interactions. The relevance o
f these de Haas-van Alphen results to strongly correlated UBe13 is also dis
cussed.