(PCT) isotherm of MgTiVZrNbHf was collected on an automated PCTPro instrument from Setaram, which allows accurate volumetric determination of the amounts of hydrogen absorbed by the sample by using calibrated volumes. The pressure was monitored with high-accuracy pressure transducers while the sample was maintained at the desired temperature and dosed with hydrogen. Prior to PCT measurements, the samples were activated in vacuum at 653 K. The enthalpy and entropy of MgTiVZrNbHf hydrogenation were determined using a published hybrid PCT/van't Hoff method by measuring a full hydrogen isotherm at 644 K, then reducing the sample temperature to 633 and 621 K and re-measuring the equilibrium pressure. The absorption PCT isotherm for the MgAlTiVCr phase was collected using an in-house built Sieverts apparatus, with similar methodology employed above, with initial temperature of 653 K, then repeating hydrogenation measurements at 673 and 693 K, re-measuring equilibrium pressure. The absorption PCT isotherm for the MgTiVCrNb was collected after activation in vacuum at 683 K, then a full hydrogen isotherm was measured by the help of an inhouse built Sieverts apparatus at 644 K.