This volume covers in detail both the fundamental and practical properties of interstitial intermetallic materials, materials which are useful as hydrogen storage materials, as rechargeable hydrogen electrodes in batteries, and as new potential hard permanent magnetic materials. Various techniques, such as magnetic, diffraction, thermodynamic, and spectral methods, for studying these materials are covered in detail at a tutorial level. The synthetic methods used to obtain these new materials are also covered in detail. It combines the expertise from two different groups of scientists working on different properties and uses of several newly developed interstitial intermetallic materials. This includes scientists working on the thermodynamics of hydrogen storage materials and rechargeable hydride batteries and also those working on hard permanent magnetic materials. The two groups provide a different, but complementary, view of the properties of interstitial intermetallic materials. The book is intended for both scientists and engineers working in the field and advanced graduate students in the fields of chemistry, physics, materials science, and materials engineering.