The localization of the electromagnetic field at the nanoscale can play a key role in many applications, such as sensing, spectroscopy and energy conversion. In the last years, great efforts have been performed to study and realize all-dielectric loss-free nanostructures to confine the radiation without the limits imposed by plasmonic systems. It has been demonstrated that an all-dielectric photonic crystal (PhC) metasurface can support bound states in the continuum (BICs) - resonant states of infinite lifetime - due to the interaction between trapped electromagnetic modes. Experimentally, this involves very narrow coupled resonances, with a high Q-factor and a possible extremely large field intensity enhancement, up to 6 orders of magnitude. Here, we demonstrate that the field enhancement in proximity of the surface can be explored to boost lightmatter interaction in spectroscopic sensing. We design and realize an …