  In the heavy-fermion metal CePdAl long-range antiferromagnetic order coexists
with geometric frustration of one third of the Ce moments. At low temperatures
the Kondo effect tends to screen the frustrated moments. We use magnetic fields
$B$ to suppress the Kondo screening and study the magnetic phase diagram and
the evolution of the entropy with $B$ employing thermodynamic probes. We
estimate the frustration by introducing a definition of the frustration
parameter based on the enhanced entropy, a fundamental feature of frustrated
systems. In the field range where the Kondo screening is suppressed the
liberated moments tend to maximize the magnetic entropy and strongly enhance
the frustration. Based on our experiments, this field range may be a promising
candidate to search for a quantum spin liquid.
