  We study the nature of the dynamics in a first-order quantum phase transition
between spherical and prolate-deformed nuclear shapes. Classical and quantum
analyses reveal a change in the system from a chaotic H\'enon-Heiles behavior
on the spherical side into a pronounced regular dynamics on the deformed side.
Both order and chaos persist in the coexistence region and their interplay
reflects the Landau potential landscape and the impact of collective rotations.
