Аннотация:Giant volume magnetostriction at room temperature is found for the first time in a La0.7Ba0.3MnO3 single crystal, achieving 2,54 x 10 ^ (-4) in a magnetic field of 8.2 kOe. An even greater value of the volume magnetoresistance, equal to 4 x 10 ^ (-4) in the same magnetic field, is observed at the Curie point Tc = 310 K. Volume magnetostriction and magnetoresistance exhibit similar dependences on tempereture and and magnetic field in the Tc-region, that is explained by the presence in this compound of a magnetic two-phase ferromagnetic-antiferromagnetic state due to strong s-d exchange.