**2. Experimental**

The Ti45Zr38Fe17 nanopowders were synthesized by mechanical alloying (MA), which was performed in the Frisch Pulverisette 7 planetary mill. Commercially available titanium (99.9%), zirconium (99.9%), and iron (99.9%) powders were used as starting materials. A mixture of the starting elements corresponding to the chemical composition of the Ti45Zr38Fe17 was placed in stainless steel vials (45 mL), which contained stainless steel balls (14 mm in diameter). An initial mass of the powder mixture before MA was 8.5 g, with the ball-to-powder weight ratio equal to 8:1. The vials containing the powder mixture and balls were evacuated by a rotary pump and then refilled with argon gas (99.999%) in a glove box. Then, gaseous argon was pumped out several times in order to extract all spurious gases from the operating atmosphere. The final argon pressure was maintained at 0.1 MPa. The ball acceleration was 15 g, while the maximum alloying time was 40 h. To avoid a temperature increase during MA, alloying periods of 0.5 h were alternated with rest periods of 0.5 h. After the first 20 h of milling, the vials were opened in a glove box and the powder was mixed. Then, the powder was subsequently alloyed for 20 h under an argon atmosphere.

The morphology of the amorphous nanopowder was studied using FEI Versa 3D scanning electron microscope (SEM). The differential scanning calorimetry (DSC) measurements were conducted under an argon gas flow at a heating rate of 5 K/min<sup>−</sup>1.

The sample was tested using neutron diffraction to check if transformation from the amorphous to the crystal structure occurred. The amorphous phase was hydrided. Hydrogen gas was introduced at a pressure of 4 MPa, and the reaction chamber was heated to 163 ◦C to initiate hydrogen uptake. The X-ray powder diffraction (XRD) patterns were collected before and after the hydrogenation of the amorphous sample to check its quality. All the above steps were performed following the procedures reported in Ref [27].

Magnetization as a function of temperature from 127 ◦C to 927 ◦C was measured using a LakeShore Model 7407 vibrating sample magnetometer (VSM) equipped with an oven under an argon atmosphere (6N) heating rate of 5 ◦C/min−<sup>1</sup> in the presence of a magnetic field of 1 Tesla. The sample was mounted with Thermeez 7020 ceramic putty on a quartz rod. The characteristic and Curie temperatures were estimated as the maximum of the first derivative of the curve.
