r script code page to Unicode

I am pulling twitter data for my Machine Learning experiment
After I get the data from my search, I want to turn it to a dataframe like this:

tweets <- searchTwitter("Bicester Village", n=1000)

df <- do.call("rbind", lapply(tweets, as.data.frame))

Twitter data arrives as list of S4 elements. I can successfully carry out experiment in my R Studio and get the results I want.

I then want to see if the data will display in sources, but I see this error:

Error

Details: "Unable to translate bytes [ED][A0] at index 1 from specified code page to Unicode."

I have tried endlesly to convert to UTF-8 (which is not a problem in R Studio), but no luck