There is more than one artist with this name:
1- A black metal band from Brazil.
2- A jazz/rock band probably from France.
3- A melodic death metal band from Germany.
4- A hard-tech/electronic one-man project from Budapest, Hungary 1- Thallium is a one-man black metal band from São Paulo, Brazil. Formed in 1995 Thallium released 1 demo "Gèvaudan", 1 full-lenght album "A Howling From a Thousand Years" and a split album with S.A.R. and Evil (Both black metal from Brazil). Thallium also participated on a Graveland tribute cd with a cover of the song "Witches' Holocaust".

Read more about Thallium on Last.fm.