Please post to the list, not to me.
The first time you did this:
pair_style eam
pair_coeff * * Ni_u3.eam Ni
The second time you did this:
pair_style eam/alloy
pair_coeff * * Ni_u3.eam
You have the pair_coeff commands exactly
backwards for the 2 pair styles.
See the pair eam doc page.
Steve