Download WMS tiles with R and use in tmap

I have access to a password protected WMS service (https://wms.swisstopo.admin.ch/) and I would like to download tiles for a bounding box with R. Then I would like to use them as background for a map created with tmap. The layer name is ch.swisstopo.pixelkarte-farbe-pk25.noscale. I don’t know where to give the authentication information.

I saw this question https://stackoverflow.com/questions/49983053/extracting-data-from-a-wms-layer but using sf::st_read() gives the following error: The file doesn't seem to exist.

I would like to have the WMS data of this extent (CRS is CH1903+):

xmin       : 2581809 
xmax       : 2583643 
ymin       : 1181706 
ymax       : 1182825 

Then, I would like to plot the map with tmap::tm_rgb() (https://www.rdocumentation.org/packages/tmap/versions/3.2/topics/tm_raster). How can I do this?