PowerShell - How can I output random number of chars from text file?

I'm trying to have random characters from text file, but something is wrong with my script.

My script:

#get the cotent of a file to a variable
$chars = Get-Content -Path C:\temp\UnicodeCharacters.txt

#get 5 random characters
$sample = $chars | Get-Random -Count 5
echo $sample

What am I doing wrong?

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