Thermal conductivity. Thermal conductivity (TC) measurements were performed using the Transient Plane Source method; 32 details of the method are given in the Supporting Information. The samples were pressed into pellets using a Carver press inside an Argon glove-box. The packing density of the pellets was determined by measuring the mass and the thickness of the pressed pellets. A Hot Disk Sensor was used which consists of an electrically conducting pattern fitted between the metal hydride pellets. The sensor applies an electrical current, high enough to increase the temperature of the samples up to several degrees. At the same time, the sensor records the resistance (temperature) increase as a function of time.