Can a Catholic marry a Mormon in a Catholic ceremony?

No. Only if the person that is Mormon became Catholic before he/she got engaged. Mormonism is considered paganism by the Catholic Church and its baptisms are declared dubious and invalid since Mormonism does not recognize the Divine Trinity of God as three equal persons in one Godhead. Hence the necessary baptismal intention is absent even though the matter and form of the Mormon practice are correct. Since Catholics cannot validly marry anyone who is not at least validly baptized, Catholics may not enter into the marriage contract with a Mormon.