Trying to import an animation as alembic. Getting hundreds of material slots... Help?

I’m using 3ds Max to create a simulation, some sort of explosion with around 200 pieces. I thought the best way to import this into unreal would be to use alembic, but when I import into unreal as a skeletal mesh I get an equal amount of materials to the number of pieces, even though the pieces are merged into 1 object. I already verified in 3ds max, there is only 1 material ID and 1 material assigned to all the pieces.

Is there anything else that I should take in mind?