We have established the material LiErF4 as a dipolar antiferromagnet with planar anisotropy, exhibiting both classical and quantum phase transitions. Where, thermal transition falls in the 2D XY/h4 universality class [1,2], while the quantum phase transition is 3D (Fig. 1). Exploiting large perfect crystals, negligible incoherent scattering, the large rare earth moment, and the existence of isotopes with and without the nuclear spins (therefore, demonstrating the effect of switching off the spin bath [3]), LiErF4 represents an ideal model, where criticality and scaling relations can be explored in great detail. We here propose the continuation of a very successful experiment on LET. This new experiment will aim to probe the critical scaling at respectively Tn and Hc.