  The Bardeen-Cooper-Schrieffer (BCS) mean-field theory of the pairing
interaction breaks down for nuclei and ultra-small metallic grains
(nanoparticles). Finite-temperature pairing correlations in such finite-size
systems can be calculated beyond the BCS theory in an auxiliary-field Monte
Carlo approach. We identify thermal signatures of pairing correlations in both
nuclei and nanoparticles that depend on the particle-number parity.
