  In most superconductors the transition to the superconducting state is driven
by the binding of electrons into Cooper-pairs. The condensation of these pairs
into a single, phase coherent, quantum state takes place concomitantly with
their formation at the transition temperature, $T_c$. A different scenario
occurs in some disordered, amorphous, superconductors: Instead of a
pairing-driven transition, incoherent Cooper pairs first pre-form above $T_c$,
causing the opening of a pseudogap, and then, at $T_c$, condense into the phase
coherent superconducting state. Such a two-step scenario implies the existence
of a new energy scale, $\Delta_{c}$, driving the collective superconducting
transition of the preformed pairs. Here we unveil this energy scale by means of
Andreev spectroscopy in superconducting thin films of amorphous indium oxide.
We observe two Andreev conductance peaks at $\pm \Delta_{c}$ that develop only
below $T_c$ and for highly disordered films on the verge of the transition to
insulator. Our findings demonstrate that amorphous superconducting films
provide prototypical disordered quantum systems to explore the collective
superfluid transition of preformed Cooper-pairs pairs.
