We report the discovery of linear magnetoelectric effect in the well-known green phase compound, Sm2BaCuO5, which crystallizes in the centrosymmetric orthorhombic (Pnma) structure. Magnetization and specific heat measurements reveal the long-range antiferromagnetic ordering of Cu2+ and Sm3+-ions moments at TN1 = 23 K and TN2 = 5 K, respectively. Applied magnetic field induces dielectric anomaly at TN1 whose magnitude increases with field, which results in significant (1.7%) magnetocapacitance effect. On the other hand, the dielectric anomaly observed in zero-applied magnetic field at TN2 shows a small (0.4%) magnetocapacitance effect. Interestingly, applied magnetic field induces an electric polarization below TN1 and the polarization varies linearly up to the maximum applied field of 9 T with the magnetoelectric coefficient {alpha} ~ 4.4 ps/m, demonstrating high magnetoelectric coupling. Below TN2, the electric polarization decreases from 35 to 29 {mu}C/m2 at 2 K and 9 T due to ordering of Sm-sublattice. The observed linear magnetoelectricity in Sm2BaCuO5 is explained using symmetry analysis.
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