We provide the first experimental evidence for a giant, conventional barocaloric effect (BCE) associated with a pressure-driven spin crossover transition near room temperature. We use magnetometry, neutron scattering and calorimetry to explore the pressure dependence of the SCO phase transition in polycrystalline samples of protonated and partially deuterated [FeL2][BF4]2 [L = 2,6-di(pyrazol-1-yl)pyridine] in pressures of up to 120 MPa (1200 bar). Our data indicate that, in a pressure change of only 0-300 bar (0-30 MPa), an adiabatic temperature change of 3 K is observed at 262 K or 257 K in the protonated and deuterated materials, respectively. This BCE is equivalent to the magnetocaloric effect (MCE) observed in gadolinium in a magnetic field change of 0-1 Tesla. Our work confirms recent predictions that giant, conventional BCEs will be found in a wide range of SCO compounds. Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))

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