I have a a few:

Angelica Selwyn is the former Arithmancy professor and now married to Emrys Selwyn. She's from ambitious, old money European purebloods. She was in Russia for the duration of her first marriage and would have been familiar in potions/alchemy elite circles through her husband 1878-1880. She came back to England in 1884. Both then and now, she has both a knack for and experience in darker magic and poisons. With her marriage a mess, it would not be difficult to get her back into darker research.

Anne Moony is going into her fifth year and already plans on taking alchemy. She's a working class halfblood and is determined to move up in the world with ambition and brains. She would already be seeking him out to improve her understanding of alchemy. She's generally respectful, if overly enthusiastic in class. She hates being babied and expects to be pushed. Impressing people she considers intelligent is still important to her.

Hermia Bonaccord is from a historic pureblood family. She's the daughter of a French diplomat. She took and loved Alchemy at Hogwarts and is now doing advanced studies at Flint Institute. She is always down for advanced research.

Themis Lyra dm'ed you about her, but Themis is a year above Sam in school and is now a colleague. We can figure out if they get along.