Get excel table from web site using httr GET

How could i extract excel table from web site, using username and password which i have using httr? I tried this, but it doesn't work:

url <- "https://ss0.corp.com/auth"
login <- "john.johnson" (fake)
password <- "67HJL54GR" (fake)

res <- GET(url, body = list(username = login, password = password))
content <- content(res, "text")

But it doesn't give me the excel table. What do i do wrong and how it must look like?