Hello @Lamonzie, Pierre (Cognizant) ,
maybe someone else can confirm, but I think it is not possible to display Excel sheet in Teams Wiki tab.
On the other hand, you can add an Excel tab in the Teams app by clicking on the "+" symbol at the top of your chosen team and choosing Excel. After you've done that, you can copy a link to the Excel tab by expanding the drop down menu of the tab and clicking on the "Copy link to tab". Now you can copy the link to the Wiki page and when someone clicks on it, Excel file you uploaded will open within the application.
Hope it helps and don't forget to upvote.
Kind regards,
Domagoj