An Iron lies on the floor North of Briana.  Return to the area North of the Nugget duo and head for the narrow tunnel on the left and you can pick up an invisible Ultra Ball off of its floor, then come out North of another electrified boulder.  Here you’ll find a battling doctor- handy for your further explorations in the cave.  In fact, every path North of the Nugget Man and Nugget Boy leads to this doctor, conveniently.

Battle: Doctor Kit (1920 Poke)
Opponent: Solosis Lv 32, Gothita Lv 32

Kit will heal your entire team just like a Pokemon Center every time you talk to him, so make note of where he is- you’ll be returning a lot.

Continue North to cross paths with another battling experimenter.

Battle: Scientist Lumi (1536 Poke)
Opponent: Joltik Lv 32, Golbat Lv 32

Head down the stairs to the West of Lumi and shove a magnetic rock further West, then follow it through and shove the other to the North and you’ll be able to reach not only a set of stairs leading further down, but also Bianca and some stairs heading up.  If you talk to Bianca, she’ll inform you that she was sent here by Professor Juniper to research the Tynamo that live in the cave- but she’s not finding many, and according to her, they’re not very strong.

Descend to the third basement level and you’ll quickly run across another musician.

Battle: Guitarist Beverly (1056 Poke)
Opponent: Zebstrika Lv 33