  We introduce pentacene-doped naphthalene as a material for diamagnetic
levitation, offering compelling applications in matter-wave interferometry and
nuclear magnetic resonance. Pentacene-doped naphthalene offers remarkable
polarizability of its nuclear spin ensemble, achieving polarization rates
exceeding 80 % at cryogenic temperatures with polarization lifetimes extending
weeks. We design a multi-spin Stern-Gerlach-type interferometry protocol which,
thanks to the homogeneous spin distribution and the absence of a preferential
nuclear-spin quantization axis, avoids many of the limitations associated with
materials hosting electronic spin defects, such as nanodiamonds containing NV
centers. We assess the potential of our interferometer to enhance existing
bounds on the free parameters of objective collapse models. Beyond matter-wave
interferometry, we analyze the prospects for implementing magic angle spinning
at frequencies surpassing the current standard in NMR, capitalizing on the
exceptional rotational capabilities offered by levitation. Additionally, we
outline a novel protocol for measuring spin ensemble polarization via the
position of the nanoparticle and conduct an analysis of dominant noise sources,
benchmarking the required isolation levels for various applications.
