  We study the influence of a close-lying non-magnetic and non-charged metal
disk on the hydration reaction of YBa2Cu3O6+d (YBCO). It has been established,
that at a distance in the range of 6 - 7 mm from the disk surface, the rate of
the hydration is significantly reduced relative to distances out of this
interval. This effect has allowed us to assume that there is an interaction
between YBCO and the disk the nature of which is still unknown. Further direct
measurements of the force acting between these bodies have been performed. A
recorded repulsive interaction with a magnitude of 6.5*10-6 N, which is 0.04%
of the sample weight, has confirmed our assumption.
