YbAl 3 is an intermediate valent compound with a Kondo temperature T K in excess of 500 K and a rather low conduction electron density of ~0.5/atom. Recent measurements are suggestive of a second energy scale T coh of order 50 K that dominates the low temperature ( T ≪ T coh ) thermodynamic properties. Previous de Haas-van Alphen (dHvA) measurements on YbAl 3 in magnetic fields to 17 T reveal a fairly simple Fermi surface with 6 branches having effective masses m* ranging from 8 to 24 m0 (see Refs. [2-3]). We report magnetization and dHvA results on YbAl 3 in pulsed magnetic fields up to 60 T. For T ≪ T coh we indeed find that the magnetization 'crosses' over from the zero field energy scale T coh to the high temperature energy scale T K at a magnetic field B * ≈ 40 T (≈ K B T coh /μB). For B > B *, we find dHvA oscillations when magnetic field is applied along the <100>, <110> and <111> directions. For magnetic field applied along <111>, the Fermi surface changes very little for B > B*, and the effective masses are all reduced by a factor of 2-3 relative to their low field values. This is due to the large change in the characteristic temperature, which goes from T coh below B * to T K above B *. We believe this is the first work to directly observe the two energy scales and to observe the crossover in the dominant energy scale as a function of magnetic field.