How to get a scientist with Psionics expertise?

After checking the code it seems like it's impossible for materialists to research psionics: In order to research Psionic Theory you need to have a scientist with the trait "Psionic Expertise". In order to unlock the trait for the pool, however, you need to already have researched "Psionic Theory".

leader_trait_expertise_psionics = {
  cost = 1
  modification = no
  icon = "gfx/interface/icons/traits/leader_traits/leader_trait_expertise_psionics.dds"
  modifier = {
      category_psionics_research_speed_mult = @categorybonus
  }
  leader_trait = yes
  leader_class = { scientist }
  prerequisites = { tech_psionic_theory }
  opposites = { 
      "leader_trait_expertise_materials" 
      "leader_trait_expertise_rocketry" 
      "leader_trait_expertise_voidcraft"
      "leader_trait_expertise_industry" 
      "leader_trait_expertise_field_manipulation"
      "leader_trait_expertise_particles"
      "leader_trait_expertise_computing" 
      "leader_trait_expertise_new_worlds"
      "leader_trait_expertise_statecraft" 
      "leader_trait_expertise_biology"
      "leader_trait_expertise_military_theory" 
  }
  # higher chance to generate techs in category psionics (done in tech-script)

  ai_categories = {
      society
  }

  ai_weight = {
      weight = 100
  }
}

As far as I've been able to tell, Scientist traits are generated randomly, not weighted based on ethos -- so the chance of a spiritualist empire generating a Psi-Specialized scientist is exactly the same as a pacifist empire.

That said, there are two ways -- either you can get extremely lucky and hire someone with the Psi. specialty directly from the leader pool, or you can get extremely lucky when a scientist levels up, and have them randomly acquire the psionic specialist trait.

I don't know the odds (except that it's a pain trying to work through all those useless scientists clogging up the pool), but I have had a survey ship scientist get the Psionic Specialist trait on level up, while playing Fanatic Materialists during a game - and subsequently slotted him into social research and got Psionic Theory several projects later. It is possible.

I’m trying the Rainbow in the Dark method now. As far as scientist I can confirm you can get Psionics via scientist level. This can be done on Ironman also. Now scientist only get traits whilst no researching science.

1. Grab a scientist just about to level and place he or she on a science ship.
2. Began an anomaly or research project.
3. At 9x% save. (If on Ironman save and quit)
4. Load save and resume time lapse long enough to complete project or anomaly.
5. Get desired trait PSIONICS, METICULOUS,SPARK OF GENIUS! (If not proceed to step 6)
6. Repeat step 5.