Use of a composition (A) having a pH of at least 8 at 25° C. containing at least 50 wt.-% of water or a water containing solvent mixture, at least 0.1 mol/m3 of at least one water soluble silicate, optionally at least one molybdate, optionally at least one phosphonate, optionally at least one azole, optionally at least one additional freezing point depressing salt, optionally at least one phosphate, and optionally at least one nitrate, as heat carrier medium for magnetocaloric materials of formula (I) (AyB1−y)2+uCwDxEz (I) where: A is Mn or Co, B is Fe, Cr or Ni, C is Ge, As or Si, D is different from C and is selected from P, B, Se, Ge, Ga, Si, Sn, N, As and Sb, E may be same or different from C and D and is selected from P, B, Se, Ge, Ga, Si, Sn, N, As and Sb.