The "magnetocaloric effect" (MCE) is based on the entropy difference encountered when themagnetic state of a material is changed and it can be used for refrigeration. However, in a reverseprocess a magnetocaloric material can also be used to directly convert heat to electricity. Theefficiency of such a thermomagnetic generator can be as high as 55.5% of Carnot efficiency.Our recent investigations revealed a sharp (first order type), but non-hysteretic (second order type) magnetic transition in manganese monoboride, which suggest tricriticality, an essential feature of reversible magnetic phase transitions with large entropy changes for applications such as magnetic cooling. Finding its origin is a useful step towards designing new functional magnets.