Many compounds made of two metals are used in the industry because at high temperatures they are harder than monometal compounds. However, at room temperature they are usually very fragile materials. Fifty years ago the physicists proposed a hypothesis that explains this fragility.
They consider that where the structure of the material is not perfect, fragility depends on the movement between the atomic layers; if they move easily, the material is not broken, but in cases where this movement is forbidden. However, this effect could not be confirmed by the absence of highly accurate electronic microscopes. Now, however, physicists have confirmed what was proposed fifty years ago.