Data for the muon-spin spectroscopy measurements and density-functional theory calculations can be found in the directories 'musr' and 'DFT', respectively, along with associated readme files.

Fig2.dat - Contains data from Figure 2. The file consists of 2 double columns titled: Temperature (K) and X (m3/mol). These represent the temperature (X) in kelvin and magnetic susceptibility (Y) in metres cubed per mole for field orientated parallel to the a-axis (H II a) and perpendicular to the a-axis (H perp a).

Fig3a.dat - Contains data from Figure 3(a). The file consists of 9 double columns titled: Magnetic field (T) and dM/dH (a.u.). These represent the magnetic field (X) in tesla and differential magnetization (Y) in arbitrary units (a.u.) for field parallel to the a-axis at temperatures of 0.34 K, 0.77 K, 1.32 K, 1.68 K, 2.00 K, 2.37 K, 3.43 K, 5.00 K and 8.78 K, measured using radio frequency susceptometry.

Fig3bc.dat - Contains data from Figure 3(b) and (c). The file consists of 3 columns titled: Magnetic field (T), M/Msat (a.u.) and d2M/dH2 (a.u.). These represent the magnetic field (X) in tesla, normalized magnetization (Y) in arbitrary units (a.u.) and second differential of the magentization (Z) in arbitrary units (a.u.) for field parallel to the a-axis at a temperature of 0.34 K as derived from radio frequency susceptometry measurements.

Fig4BottomPanel.dat - Contains data for bottom panel of Figure 4. The file consists of 7 columns. The first contains the magnetic field (X) in tesla with columns 2 to 7 (Y) containing the ESR measured transmission spectrum (dI/dH) in arbitrary units (a.u.) for field parallel to the a-axis at temperatures of 3.7 K, 6.1 K, 7.1 K, 8.1 K, 9.0 K, 10.1 K, 12.2 K measured at a frequency of 9.35 GHz.

Fig4TopPanel.dat - Contains data for top panel of Figure 4. The file consists of 3 columns. The first contains the magnetic field (X) in tesla with the ESR measured transmission spectrum (dI/dH) in arbitrary units (a.u.) for field parallel to the a-axis (H II a) in column 2 (Y) and b-axis (H II b) in column 3 (Z) measured at a temperature of 4.0 K and at a frequency of 9.35 GHz.

Fig5.dat - Contains data for Figure 4. The file consists of 2 double columns. The first column contains the magnetic field (X) in tesla with the second column (Y) containing the ESR measured transmissittance in arbitrary units (a.u.) at frequencies of 60 GHz, 105 GHz, 130 GHz, 180 GHz. Measurements made with field parallel to the a-axis at a temperature of 1.8 K.

Fig6.dat - Contains data from Figure 6. The file consists of 4 double columns titled: Magnetic field (T) and Frequency (GHz). These represent the magnetic field (X) in tesla and frequency (Y) in giga hertz for field parallel to the a-axis. Each double column corresponds to the field-frequency position for the ESR resonance in a partiuclar branch. These are the tau, G1, G2 and G2 modes described in main text of the paper.

Fig11.dat - Contains data from Figure 11. The file consists of 2 quadruple columns titled: Magnetic field (T), Field err (T), Temperature (K) and Terr (K). These represent the critical magnetic field in tesla, it's associated error, the temperature these critical fields were measured at in kelvin and the associated error in the temperature. The first four columns correspond to critical fields determined with field parallel to the a-axis (H II a) and the second with field parallel to the b-axis (H II b).

FigS1a.dat - Contains data for Figure 1a in the supplemental information. The file consists of 3 double columns titled: Temperature (K) and X (m3/mol). These represent the temperature (X) in kelvin and magnetic susceptibility (Y) in metres cubed per mole for field orientated parallel to the a-axis (H II a) and in two orientation perpendicular to the a-axis (orientation 1 and 2).

FigS1b.dat - Contains data for Figure 1b in the supplemental information. The file consists of 3 double columns titled: Magnetic field (K) and M (muB per ion). These represent the magnetic field (X) in tesla and magnetization (Y) in bohr magnetons per ion for field orientated parallel to the a-axis (H II a) and in two orientation perpendicular to the a-axis (orientation 1 and 2).

FigS2.dat - Contains data for Figure 2 in the supplemental information. The file consists of 2 triple columns titled: Field orientation (degrees) and two g-factor columns. These represent the orientation of the magnetic field relative to the crystallographic axis (X), the measured g-factor moving from the a to b axis (Y) and the measured g-factor moving from the b to c axis (Z). The first three columns are for measurements made at 295 K and the second three are for measurements made at 20 K.