The hydrogen desorption properties of the Mg-10at.%Sc solid solution in the form of filings were measured using Sieverts' apparatus. It was found that the amount of desorbed hydrogen in the temperature range 350-400 °C was only about two-thirds of that expected from the formula (Mg-Sc)H2. The curve of hydrogen concentration versus pressure at constant temperature shows a conspicuous sloping plateau. It is argued that this behaviour is the simple consequence of the strong bond between the hydrogen atom and the neighbouring scandium atom, if any. The strong bond is attributed to the outer electron of the scandium atom in the solid solution which has significant d character. To support this view the electronic structure of the dilute Mg-Y alloy was studied by measuring the de Haas-van Alphen effect. According to the phase shift analysis applied to the de Haas-van Alphen results, the number of d electrons for each yttrium atom is 0.5 in the magnesium alloy.
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