Effects of temperature and pressure on magnetic, elastic, structural, and thermal properties of ${\mathrm{T}\mathrm{b}}_5{\mathrm{S}\mathrm{i}}_2{\mathrm{G}\mathrm{e}}_2$ have been studied by means of macroscopic (thermal expansion and magnetization) and microscopic (neutron powder diffraction) techniques. We present evidence that the high-temperature second-order ferromagnetic transition can be coupled with the low-temperature first-order structural phase change into a single first-order magnetic-crystallographic transformation at and above a tricritical point in the vicinity of 8.6 kbar. This pressure-induced coupling has a remarkable effect on the magnetocaloric effect, transforming ${\mathrm{T}\mathrm{b}}_5{\mathrm{S}\mathrm{i}}_2{\mathrm{G}\mathrm{e}}_2$ from an ordinary into a giant magnetocaloric effect material.

• Received 20 May 2004
• Publisher error corrected 28 September 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.137201