Read SDMX into a Dataframe R

Question

I am struggling with using readSDMX into a dataframe. My code is below, along with the error. Any help on this would be greatly appreciated. This is my first time using the RSDMX library, so pretty new to this.Thanks in advance!

tmp <- tempfile()
download.file("https://markets.newyorkfed.org/api/ambs/all/results/summary/search.sdmx.xml? 
               startdate=03/01/2020&enddate=04/05/2020", tmp) 


fedops <- readSDMX(tmp,isURL = FALSE)
fedops2 <- as.data.frame(fedops)

Error in t.default(attrs) : argument is not a matrix