akin to the Ising exchange of spin ice [@Ross11a; @Cao09; @Thompson11b], despite an XY-like anisotropy perpendicular to the local $<111>$ directions [@Hodges01; @Malkin04]. At low temperature, using a model Hamiltonian with anisotropic exchange parameters deduced from experiments, a first-order phase transition towards a long-range ferromagnetic order is predicted [@Applegate12; @Chang12; @Savary13; @Han13].

Experimentally, the existence of a long-range magnetic ordering in this compound is debated, suggesting a fragile ground state with respect to perturbations. In an early study, a peak was observed around 210 mK in the specific heat of a polycrystalline sample [@Blote69]. It was later shown to be associated with an abrupt slowing-down of the fluctuations in the low temperature phase thus suggesting a first-order transition [@Hodges02].

Below the transition, depending on the nature of the samples (single crystal or polycrystal) and the crystal growth conditions, different results have been obtained. Some neutron scattering measurements demonstrate ferromagnetic long-range order (LRO) [@Yasui03; @Chang12] while others do not [@Gardner04; @Bonville04; @Ross09]. A discrepancy is also observed in muon spin relaxation measurements ($\mu$SR) where an anomaly at the transition is present [@Hodges02; @Chang13] or not [@DOrtenzio13]. In the meantime, it was shown that the peak in specific heat strongly depends on 