  We show for the intermediate valence compound YbAl$_{3}$ that the high field
(40 $\lesssim B \lesssim$ 60T) effective masses measured by the de Haas-van
Alphen experiment for field along the $<111>$ direction are smaller by
approximately a factor of two than the low field masses. The field $B^{*} \sim$
40T for this reduction is much smaller than the Kondo field $B_{K} \sim
k_{B}T_{K}/\mu_{B}$ ($T_{K}\sim$ 670K) but is comparable to the field
$k_{B}T_{coh}/\mu_{B}$ where $T_{coh}\sim$ 40K is the temperature for the onset
of Fermi liquid coherence. This suggests that the field scale $B^{*}$ does not
arise from 4$f$ polarization but is connected with the removal of the anomalies
that are known to occur in the Fermi liquid state of this compound.
