magnetic susceptibility show well defined structural and antiferromagnetic transitions at temperatures of $T_{OO} \approx 63 \pm 1 \,\textrm{K}$ and $T_N \approx 42\,\textrm{K}$, respectively, demonstrating the high quality of the crystals. Using neutron diffraction on the single-crystals, the space group was confirmed to be face-centred cubic $\mathrm{Fd\bar{3}m}$ above $T_{OO}$ and tetragonal $\mathrm{I4_{1}/a}$ below $T_{OO}$ [^1].

At the neutron diffractometer MIRA [@MIRA; @MIRAnew], the temperature ($T$) dependence of the lattice constants was measured using $\theta$-$2\theta$ scans around the (220) Bragg reflections of the single-crystals. The volume of the unit cell was determined to be $V \approx 593\,{\mbox{\normalfont\AA}}^3$. The very weak $T$-dependence of $V$ (Fig. \[fig:lattice\]) is compatible with the results of Refs. .

![ \[fig:lattice\]$(a)$ Temperature-dependent change of the unit cell volume $V$ as determined using neutron diffraction. Note that the error bars include the instrument resolution as systematic error. $(b)$ The intensities of the $\vec{Q}$=(110) and the $\vec{Q}$=(004) Bragg reflections as a function of temperature illustrating the structural transition at T$_{OO}$=63 K and magnetic ordering temperature of T$_{N}$=42 K. The data in panel $(b)$ was taken using the RITA spectrometer in two-axis mode with E$_{i}$=5 meV. The (004) Bragg peak was measured at the (002) position using $\lambda/2$ with the scattered 