  Two-component fermions are known to behave like a gas of molecules in the
limit of Bose-Einstein condensation of diatomic pairs tightly bound with
zero-range interactions. We discover that the formation of cluster states
occurs when the effective range of two-body interaction exceeds roughly $0.46$
times the scattering length, regardless of the details of the short-range
interaction. Using explicitly correlated Gaussian basis set expansion approach,
we calculate the binding energy of cluster states in trapped few-body systems
and show the difference of structural properties between cluster states and
gas-like states. We identify the condition for cluster formation and discuss
potential observation of cluster states in experiments.
