If I see a character I can't enter in someone's code, I think I'll run away. It's cool and all for your code, but sooner or later someone else is going to have to deal with it.
If your audience is mostly programmers then just use `*`
If your audience is physicists or mathematicians then `×` or `·` may be a better fit.
When turning a math expression into code, it is often handy if the code looks a lot like the expression. Even better if you can just copy and paste it. It's hard to translate an expression wrong if you aren't translating it at all.