Split body Creo 2.0

If your goal is to maintain a link between the two parts, I would suggest using inheritance for the second part.

Split the original part in the first direction.  Suppress the split and create the spit in the other direction.  Suppress the second split and resume the first.  Start a new part and create a merge inheritance using the original part.  In the inheritance, suppress the first split and resume the second split.

@kdirth has presented one solution using merge/inheritance.  You must have the AAX extension license or equivalent to use merge functionality.

I would offer a slight variation on the use of merge functionality that can save some effort. This is more efficient when splitting a model into many parts. 

1. Create the master model defining the geometry to be split and the geometry needed to create the split
2. Create a derivative (new part) of the master using merge function and save the part and create the cut (split)
3. Save a copy of the derivative part and reverse the direction of the cut

You now have two parts driven by the master model. See enclosed video for details.