Antimatter

Known reactions that create antimatter: There are none yet, except for particle accelerators.
There are some theories though, and I will post them as I find them.
The best reaction would be a one step reaction. Find a material and mix it with another material in the perfect environement and it will make large quantities of antimatter. That is the ideal circumstance.
It's not very far fetched to imagine this when there are fusion reactions that transform particles into different particles, and that there are chemical endothermic reactions and exothermic reactions. Looking at the real properties of barium titanate makes you question what can and cannot be done theses days also.

One theory has to do with the material known as helium 3 that we can acquire on the moon, but if we used that for a stable fusion reaction and put lots of money into fusion research then we may well find new reactions that have byproducts which include antimatter.

The current way of making antimatter is to accelerate electrons until they collide and create a new negatively charged anti-hydrogen atom. But there may be other more efficient and predictable methods that we may find in the future that can be scaled to mass produce antimatter. As long an fusion energy works and gets funding for new nuclear physics experiments beyond fusion.

Antimatter occurs naturally in the van allen belts of earth and also at gas giants like jupiter. See: "antimatter" on wiki under "cost".And if we can somehow find a way to store the antimatter(encapsulated in neutrons) and use it, then we may have free energy if the antimatter can be reused based only on its "potential energy" which has reverse effects in the physical universe making new electrical and particle aplications and experimants possible with this new material of totally alien properties. See: "magic rectangle"

Also see my other antimatter post.
And "The final revolution is...".